Definitions

Definitions

I use a lot of fly fishing, entomology, and photography jargon on this site. The site incorporates these definitions wherever they're used, but it might help some people to see them all listed in one place.

• abdomen (abdomens, abdominal) - The rear and usually the longest (ten-segmented in mayflies) portion of an insect's body, to which the tails are attached.
• abdominal setal areas (abdominal setal area, abdominal (sa)1, abdominal (sa)2, abdominal (sa)3) - Some caddisfly larvae have setal warts on first abdominal segment which are reminiscent of those commonly used for identification on the metanotum. They are similarly denoted sa1, sa2, and sa3, and may appear on both the dorsal and ventral surfaces of that segment. Both dorsal sa1 and ventral sa2 may be found on slightly raised, central bumps, whereas sa3 is always lateral. The boundaries between these areas are not always clearly delineated, if at all.
• acuminate (acuminately) - Tapering to a long point.
• acute@ (acutely@) - Characterized by a sharp angle, typically less than 90º, although sometimes used in a relative way to distinguish very sharp from somewhat less sharp angles.
• adventive - Introduced but not fully established, used in reference to organisms living outside their native range.
• aedeagus (aedeagal) - The reproductive (copulatory) organ of male arthropods
• alimentary canal - The food tube traversing the body from the mouth to the anus.
• alkaline (alkalinity) - Having a pH higher than 7 (opposite of acidic). Moderately alkaline water is ideal for trout because it's better for the growth of phytoplankton, the usual base of the aquatic food chain, and that's good for the growth of everything higher up the chain, including trout.
• alula - Membraneous lobes at the posterior angle of the wing base in some Diptera
• amphipneustic - Having a respiratory system with two spiracles, one on the mesothorax and one on the posterior end of the abdomen.
• anal cell@p (anal cells@p) - A cell near the posterior part of the base of the wing, from which the anal veins appear to arise.
• anal cell@t (anal cells@t, first anal cell, first anal cell@t, second anal cell, second anal cell@t) - The anal cell (denoted ac) is a cell formed by crossveins closing the space between anal veins, including sometimes at their bases, creating of a loop from which the veins appear to arise. Some sources may refer to the two cells basal of the one labeled in the forewing illustration as the first and second anal cells.
• anal claw (anal claws) - Hook-like claws located on appendages of the last abdominal segment in some larvae, most commonly caddisfly larvae.
• anal division - A split into two branches in the posterior end of the body of many Diptera larvae.
• anal gill (anal gills) - Gills located at the tip of the abdomen.
• anal papilla (anal papillae) - Any of various tubes or lobes arising near the anal opening or posterior end of the abdomen, meaning slightly different things for different taxa.
• anal region (anal regions) - The most posterior portion of an insect's wings, containing the anal veins.
• anal vein@e (anal veins@e, vein A_1@e, A_1 vein@e, A_1@e, vein A_2@e, A_2 vein@e, A_2@e) - The anal veins (denoted A₁, A₂, etc.) are all the longitudinal veins posterior to the cubitus, often occupying only a small portion of the wing in mayflies.
• anal vein@p (anal veins@p, anal region@p, vein A_1@p, A_1 vein@p, A_1@p, vein A_2@p, A_2 vein@p, A_2@p, vein A_3@p, A_3 vein@p, A_3@p) - The anal veins (denoted A₁, A₂, etc.) are all the longitudinal veins posterior to the cubitus. Stonefly hind wings are typically notched or folded near the posterior branch of the cubitus, and the anal veins are found beyond that fold in the anal region.
• anal vein@t (anal veins@t, vein 1A@t, 1A vein@t, 1A@t, vein 2A@t, 2A vein@t, 2A@t, vein 3A@t, 3A vein@t, A3@t, vein 4A@t, 4A vein@t, A4@t, vein 5A@t, 5A vein@t, A5@t) - The anal veins (denoted 1A through 5A in caddisflies) are longitudinal veins posterior to the cubitus. Caddisfly forewings have 3 anal veins, which typically coalesce into a single vein reaching the wing margin, forming a characteristic forked shape. Caddisfly hind wings have 1 to 5 anal veins, which all reach the wing margin.
• anastomosed (anastomoses, anastomose, anastomosing) - Anastomosed wing veins branch out and rejoin, often creating the appearance of irregular subdivisions in contrast to the commonly expected regular pattern of veins.
• angulate - Having an edge with a well-defined angular bend.
• annulate (annulated, annulatus, annulus) - Shaped like a ring, or formed of or marked with ring-like segments.
• anterior (anteriorly, anterad) - Toward the front of an organism's body. The phrase "anterior to" means "in front of."
• anterodorsal (antero-dorsal, anterodorsally, antero-dorsally) - Toward the top and front of a body or structure.
• anterolateral (anterolaterally, anterolad, antero-lateral, antero-laterally) - Located to the front and side.
• anteromesal (anteromesally, anteromedial, anteromedially, anteromedian, antero-mesal, antero-mesally, antero-medial, antero-medially) - Located in the middle on the lateral axis, but toward the anterior end of a body or structure.
• anteronotal - Located toward the anterior edge of the notum.
• aperture (apertures) - The aperture is one of the main settings a camera or photographer determines before taking a picture. It is the diameter of the opening in the inside of the lens through which light can pass, and it varies from picture to picture.
• apex (apices, apical, apically) - The apex is uppermost, outermost, or culminating point; the tip. Features located at the apex are described as apical.
• apicolateral (apico-lateral, latero-apical, apicolaterally, apico-laterally, latero-apically) - Located to the side of a structure near its tip, or apex.
• apneustic - Having no functioning respiratory spiracles, meaning the tracheal system does not open externally.
• apotome - A v-shaped subdivision in body parts covered by a membraneous fold.
• appressed - Pressed together.
• arcuate (arcuately) - Arched or bow-like in shape.
• arculus@p - In stoneflies, the arculus (denoted ar) is a crossvein which connects the radius to the cubitus near the base of the wing. The media may appear to begin at the arculus, but in fact it begins more basally and part of the arculus forms part of the media.
• arculus@t - An inflexed (subtly, broadly indented) point on the posterior edge of a caddisfly forewing, where vein Cu₂ hooks backward to the wing edge and often fuses with the end of vein 1A.
• arista - In some Diptera, reduced flagellomeres of antenna following the usually enlarged, first flagellomere (beyond the pedicel) of the antenna.
• arolium - In some adult Diptera, a median, more or less saclike protrusion from the end of the pretarsus.
• aslant - slanted
• asynchronous - The same generation hatching at different times.
• atrophy (atrophied) - A body part which has shrunk or degenerated into a dysfunctional state is said to have atrophied. The mouth parts in adult mayflies are good examples.
• attingent - Touching, i.e. contiguous.
• attractor (attractors) - Flies not designed to imitate any particular insect, but to incorporate characteristics attractive to trout. When trout aren't feeding selectively, attractors often outperform careful imitations as searching patterns because they are easier to see and incorporate more strike-triggering characteristics. They include legends like the Adams, Bivisible, and Royal Wulff.
• auxilia (auxiliae, auxillae) - A small plate beneath the base of a pretarsal claw.
• axillar fold (jugal fold) - A fold located behind the last anal vein in some insect wings.
• basal (basally, basad) - close to the base; root or beginning
• basalis - When separate sclerites are distinguishable on the mandible, the basalis is the principal one, to which all other parts are jointed. It is comparable to the stipes on the maxilla.
• basisternum (basisternal, basisternite) - The primary, central plate in the anterior portion of an abdominal sternum.
• basolateral - Located to the side, near the base.
• basoventral - Located on the bottom near the base.
• behavioral drift (behavioral drifting) - The nymphs and larvae of many aquatic insects sometimes release their grip on the bottom and drift downstream for a while with synchronized timing. This phenomenon increases their vulnerability to trout just like emergence, but it is invisible to the angler above the surface. In many species it occurs daily, most often just after dusk or just before dawn.
• biconcave - Having a concave shape on both sides.
• bicornuate - Having two horns or horn-shaped processes.
• bidentate - Having two teeth.
• bifid - Forked or otherwise divided into 2 distinct parts.
• bifurcate (bifurcated) - Split into two parts or branches.
• bilamellate - Comprised of two lamellae.
• bilobed - Made of two distinct lobes.
• bistre - A dark, grayish brown color.
• bivoltine - Producing two generations per year.
• brachypterous (brachyptery) - Having short or or abbreviated wings.
• brood@ (broods@) - When a species produces more than one generation per year, each one is called a brood.
• bulla (bullae, bullar) - An expanded, often lighter-colored point in a wing vein, usually about half-way up the front edge of a mayfly wing, in the subcostal vein (the first major vein not on the edge) and often in several other longitudinal veins alternating in a line near the middle of the wing. A bulla is a weakly chitinized point that allows the wing to flex during the upward stroke in flight to reduce air resistance, while the stiffening during the downward stroke to provide more lift.
• burnt-sienna (burnt sienna) - A pale reddish-brown color.
• burnt-umber (burnt umber) - A rich, reddish-brown color.
• calypter (calypteres) - The calypteres are two posterior lobes of the posterior margin of the forewing of some flies, located between the extreme posterior wing base and the alula.
• canine (canines) - A heavily chitinized spine arising from the mandible or maxilla, often being the main or largest "tooth" at the tip of the structure. Often used in reference to mayfly or stonefly nymphs.
• carapace (carapaces) - A hard, protective shell on the back of an animal. In mayflies, this refers to the enlarged section of the mesonotum which forms the "humps" of Baetisca nymphs.
• carina (carinae) - A narrow keel-shaped anatomical ridge.
• caudal (caudally, caudad) - Directed toward or in the vicinity of the tails or posterior tip of the body.
• caudal cercus (caudal cerci) - A technical term for tail.
• caudal filament (caudal filaments) - A technical term for tail. It may refer to any of the tails of a three-tailed insect, including the middle.
• cephalad - Toward the head or anterior end of the body.
• cephalic - Belonging or attached to the head.
• cephalopharyngeal skeleton - In some larval Diptera, a portion of head forming a heavily sclerotized, internal pharyngeal skeleton withdrawn into the thoracic segments.
• cercus (cerci, cercal) - The left and right "tails" of an insect are known as the cerci or caudal cerci. The middle tail of a three-tailed insect is not.
• cervical (cervix) - In the vicinity of the neck.
• cervical gills (cervical gill) - Gills located on the head, near the "neck," i.e. the membrane that separates the head from the thorax.
• chelate - Pincer-like, having two opposable claws.
• chitin (chitinous, chitinized) - The tough natural polymer which hardens the exoskeletons of insects and serves numerous other important biological functions.
• chloride epithelium (chloride epithelia) - An area of of tissue specialized for ion absorption on the surface of the skin of many caddisfly larvae, evident as light-colored patch (typically oval-shaped) surrounded by a very thin line of darker, sclerotized tissue. Chloride epithelia are most often found on the ventral abdominal segments but may also be found on the dorsal or lateral aspects.
• chorion - The outer shell or covering of an insect egg.
• circlet hair (circlet hairs) - Small hairs forming rings, e.g., around a segment of an insect's tail.
• clasper (claspers) - The claspers, also known as forceps, are a pair of appendages beneath the tip of the abdomen of male mayfly adults, which are used to grab onto the female while mating.
• clavate - Club-like, i.e. thickening gradually toward the tip.
• clothing hair (clothing hairs) - Fine hairs, or setae, covering the surface of an insect body or body part thickly enough to appear like a soft coating.
• clypeus (clypeal) - That part of the insect head below the frons, to which the labrum is attached anteriorly.
• compound eye (compound eyes) - The eyes of many arthropods, including insects and crustaceans, are composed of anywhere from 12 to 1,000 facets called ommatidia. These are called compound eyes.
• conical mesonotal projection (conical mesonotal projections) - small cone shaped spike sticking up from the top and front part of the middle thorax segment.
• coniform - Cone-shaped.
• cord@ (cords@, anastomosis@t, chord, chords, cord@t, chords@t) - In insect wings, the cord (sometimes also spelled chord, or referred to as the anastomosis) is an apparent, jagged, transverse line across the wings where the major crossveins align with the bases of the main forks of the longitudinal veins. It is especially noteworthy as an identifying characteristic in caddisfly forewings.
• costa@e (costal@e, costal vein@e, vein C@e, C vein@e, C@e) - The costa (denoted C) is the first (anterior) major longitudinal wing vein. In mayflies, it forms most or all of the front edge of the forewing. It is a ridge vein (+).
• costa@p (costal@p, costal vein@p, vein C@p, C@p) - The costa (denoted C) is the first (anterior) major longitudinal wing vein. In stoneflies, it forms most or all of the front edge of each wing.
• costa@t (costal@t, costal vein@t, vein C@t, C@t, C vein@t) - The costa (denoted C) is the first (anterior) major longitudinal wing vein. In caddisflies, it forms most or all of the front edge of each wing.
• costal angle (costal angles, apical angle, apical angles) - The angle of the turn in the edge of an insect's wing from the anterior, costal margin into the distal edge of the wing.
• costal angulation - A bend in the front margin of the hind wing of some insects, which is used as an identifying characteristic for some mayflies.
• costal border - The front edge of a wing.
• costal cell@e (costal cells@e) - Cells in the wing formed by the crossveins between the costa and subcosta.
• costal crossvein (costal crossveins, costal crossvein@e, costal crossveins@e, costal cross veins, costal cross veins@e, costals, costals@e) - Crossveins in between the leading edge of the wing and the first longitudinal vein inside the wing, i.e. between the costa and subcosta. Some older sources may simply refer to them as "costals."
• costal margin - The area near the front edge of the wing.
• costal process (costal processes) - A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal projection.
• costal projection (costal projections) - A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.
• costal space@e - The area between the costa and subcosta.
• costal space@p - The area between the costa and subcosta.
• costal space@t (costal space@t) - The area between the costa and subcosta.
• costal vein (costal veins) - The thick vein which forms the front edge of an insect's wing.
• costo-apical space (costal-apical region, costo-apical region, costal-apical space, costo-apical area) - The space along the front edge of the wing near the wingtip.
• coxa (coxae, coxal) - The basal segment of an arthropod's jointed leg; comes from the Latin word for "hip." Although a part of the leg, it may look more like a socket on the body to which the "actual" leg connects.
• creeping welt (creeping welts) - In some Diptera larvae, transverse swollen ridges on the anterior ventral margins and sometimes the anterior dorsal margins of abdominal segments (usually segments I--VII), which have rows of minute,
  sclerotized hooks.
• crescentic - Crescent-shaped.
• cribiform - Pierced with numerous small holes, like a sieve.
• cripple (cripples) - In fly fishing, a cripple is any insect which has been injured or deformed so that it cannot escape the water. This may include stillborn emergers or fully emerged adults which have been damaged, often by wind or waves, so that they can no longer fly. Trout often favor eating crippled insects.
• crochet (crochets, crocheted) - Curved hooks, typically found on the end of various insect appendages, but not used to refer to ordinary claws on legs.
• crossvein (crossveins, cross vein, cross veins) - Short cross-wise veins in an insect wing which connect the long longitudinal (length-wise) veins.
• cubital - The cubital region is the lower back corner of an insect's wing, through which the cubitus and other cubital veins run.
• cubital intercalary vein@e (cubital intercalary veins@e) - Cubital intercalary veins are longitudinal veins unattached to the wing base (except perhaps by crossveins) and located in between CuA and CuP.
• cubital vein (cubital veins) - Insect wing veins which stem from the cubitus.
• cubito-anal crossvein@p (cubitoanal crossvein@p, cu-a crossvein@p, crossvein cu-a@p, cu-a@p) - The cubito-anal crossvein (denoted cu-a) is a crossvein connecting the cubitus to the first anal vein, typically very close to the base of both veins in stoneflies.
• cubito-anal crossvein@t (cu-a crossvein@t, crossvein cu-a@t, cu-a@t) - The cubito-anal crossvein (denoted cu-a) is a crossvein connecting the cubitus to the first anal vein.
• cubito-anal region (cubitoanal region) - The area encompassing both the cubitus and anal veins in an insect's wing.
• cubitoanal crossvein (cubitoanal crossveins, cubito-anal crossvein, cubito-anal crossveins) - A short crossvein connecting the cubitus to the anal veins in the vicinity of the anal cell in a stonefly forewing.
• cubitus - The fifth longitudinal vein connecting the wing margin to the wing base.
• cubitus - The sixth longitudinal vein of an insect wing immediately posterior to the media (M).
• cubitus anterior@e (vein CuA@e, CuA vein@e, CuA@e, vein Cu_1@e, Cu_1 vein@e, Cu_1@e) - The cubitus anterior (denoted CuA) is the next major longitudinal vein behind the medius posterior. It may be branched or unbranched. It is a ridge vein (+). Very old sources might denote it Cu₁.
• cubitus posterior@e (vein CuP@e, CuP vein@e, CuP@e, vein Cu_2@e, Cu_2 vein@e, Cu_2@e) - The cubitus posterior (denoted CuP) is the next major longitudinal vein behind the cubitus anterior. It does not fork. It is a furrow vein (–). Very old sources might denote it Cu_2.
• cubitus@p (vein Cu@p, Cu vein@p, Cu@p, vein Cu_1@p, Cu_2 vein@p, Cu_2@p, vein Cu_1@p, Cu_2 vein@p, Cu_2@p) - The cubitus (denoted Cu) is the fifth major longitudinal wing vein in insects, located behind the media. In stoneflies, it usually branches near the base into an anterior for Cu_{1 and posterior fork Cu2.}
• cubitus@t (vein Cu@t, Cu vein@t, Cu@t, vein Cu_1@t, Cu_1 vein@t, Cu_1@t, vein Cu_2@t, Cu_2 vein@t, Cu_2@t, vein Cu_1a@t, Cu_1a vein@t, Cu_1a@t, vein Cu_1b@t, Cu_1b vein@t, Cu_1b@t) - The cubitus (denoted Cu) is the fifth major longitudinal wing vein in insects, located behind the media. In caddisflies, its anterior branch Cu₁ arises from a point on the media near or at its base, and the posterior branch Cu₂ arises separately from the base of the wing. The anterior branch Cu₁ is subdivided into two branches Cu_1a and Cu_1b, while the posterior Cu₂ is unbranched. In the forewing, the tip of Cu₂ curves backward to the wing edge at a slightly inflexed point called the arculus.
• cuticle (cuticles, cuticula, cuticular) - An often multi-layered secretion of the epidermis, making up the entire body covering of an insect and most of the integument.
• cyclorrhaphous - Members of the Diptera suborder Brachycera in which the pupa or adult escapes from the last larval skin by pushing off a circular lid or covering.
• dead drift (dead-drifting, dead-drift, dead drifting) - The manner in which a fly drifts on the water when not moving by itself or by the influence of a line. Trout often prefer dead-drifting prey and imitating the dead-drift in tricky currents is a major challenge of fly fishing.
• decurrent - Closely attached to and running down another body.
• denticle (denticles) - Small tooth-like projects, often appearing like serrations on the tarsal claws of certain mayfly nymphs.
• detritivore (detritivores) - eater of plant and animal debris
• detritus - Small, loose pieces of decaying organic matter underwater.
• diapause - A state of complete dormancy deeper even than hibernation. While in diapause, an organism does not move around, eat, or even grow. Some caddisfly larvae enter diapause for a few weeks to several months. Some species of microscopic zooplankton can enter diapause for several hundred years.
• dichoptic - Having compound eyes distinctly separated from each other, i.e. not touching.
• digitate - Divided into finger-like processes.
• digitate-lobe - A thumb-like lobe appearing on the labial palpi of some Baetidae nymphs.
• disc@ (disc@e, disc@t, disc@p, discs@, discs@e, discs@t, discs@p) - The area in the middle of an insect's wing.
• discal - On or relating to the disc, or upper central surface, of a body part, often used to refer to the central area of an insect wing.
• discal area (discal areas) - The middle of an insect's wing.
• discoidal cell@t (dc@t, cell dc@t, dc cell@t) - The discoidal cell (denoted dc) is a distinctive cell in caddisfly wings, formed by the forks of the radial sector being closed apically by the sectorial crossvein.
• distal (distally) - Far from the point of attachment or origin; near the tip.
• dorsal (dorsum, dorsally) - Toward the top of the body.
• dorsolateral (dorsolaterally) - Located to the side near the dorsal (top) surface of a body or structure.
• dorsoventral (dorsoventrally) - The dorsoventral axis is the axis running from the top to the bottom of the body; for example, a has a flounder is dorsoventrally flattened body shape.
• dun@ (duns@) - Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.
• ecdysial scar - In some insects, a scar in new cuticle representing a former spiracle.
• ecdysis - the process of casting the skin; moulting
• eclosion (eclose) - the act of emerging from the pupal or nymphal case or hatching from the egg
• elytroid - The gills on some mayfly nymphs which are enlarged as shields to protect the other gills (as on Tricorythodes and Eurylophella nymphs) are called elytroid gills.
• elytron (elytra) - The hard, leathery forewing of beetles, which as a covering for the hind wings. Colloquially, this is the part that forms the main "shell" over the body when not flying.
• emarginate (emargination) - Having a notched edge.
• emergence@ (emergences@) - The transformation of a nymph or pupa into the adult winged stage of an insect. The term may refer to the emergence of an individual, or the daily or yearly event in which all individuals of a species emerge.
• empodium - In adult Diptera, an unpaired median process arising from the ventral or plantar region of the arolium.
• endemic - where found; native to; belonging exclusively to or confined to a particular place
• epicranium (epicranial) - The upper part of the head from the frons to the neck, including frons, vertex and genae.
• epiproct (epiprocts) - A single appendage projecting dorsally from the tenth abdominal segment.
• episternum - The anterior sclerite on the pleuron.
• eusternum (eusternal) - The anterior plate of the sternum.
• eversible - Able to be turned inside-out.
• excision - A deep notch or other cut-out part.
• excrescence (excrescences) - An outgrowth or elevated spot, usually abnormal, and sometimes very subtle.
• exserted (exsert) - Sticking out. The opposite of inserted.
• femur (femora, femoral) - The main segment of an insect's leg close to the body, in between the tibia and the trochanter.
• ferruginous - Reddish brown; rust-colored.
• fibril (fibrils) - A fine, narrow, fibrous, structure, as in the branches of some insect gills.
• fibrilliform - Made of multiple smaller fibrils, giving a branched appearance.
• filiform - Insect gills which are filamentous (feathery or thread-like) are described as filiform.
• flagellomere (flagellomeres) - The individual segments of the third, typically longest, part of an insect's antenna, the flagellum.
• flagellum - The third part of an insect's antennae, beyond the pedicel, often the longest and consisting of many segments called flagellomeres.
• flange (flanges) - A flat rim that stretches beyond the end of a structure.
• flight period (flight period) - The span of time that the adults of an adult aquatic insect species are active and flying around, in between emergence and death. It may refer to the average adult lifespan of the individuals of that species, or to the total length of time for which at least some of them are active.
• fluting - Alternating ridges and valleys in the wings of insects. Many wings, especially in mayflies, dragonflies, and damselflies, are not as flat as they appear at first glance, but instead contain subtle accordion-like folds the help control how they flex during flight. Ridge veins are convex in the dorsal view and denoted with (+), and valleys or furrow veins are denoted (–).
• follicle cell (follicle cells) - Cells in the ovaries that contain the immature eggs.
• forcep (forceps) - The claspers, also known as forceps, are a pair of appendages beneath the tip of the abdomen of male mayfly adults, which are used to grab onto the female while mating.
• forecoxa (forecoxae, fore coxa, fore coxae) - The forecoxae are the coxae on the forelegs.
• forefemur (forefemora, forefemoral, fore femur, fore femora, fore femoral) - The femur on an insect's front set of legs.
• foreleg (forelegs, fore leg, fore legs) - The front (anterior) legs of an insect.
• foretarsus (foretarsi, foretarsal, fore tarsus, fore tarsi, fore tarsal) - The tarsi on the forelegs.
• foretibia (foretibiae, foretibial, fore tibia, fore tibiae) - The foretibiae are the tibiae on the forelegs of an insect.
• foretrochantin (foretrochantins, fore trochantin, fore trochantins) - The trochantin on the foreleg.
• forewing (fore wing, forewings, fore wings) - The front pair of wings of an insect, which are attached to the mesothorax, the same thoracic segment that bears the middle pair of legs. In mayflies, these are the main, large wings. In caddisflies, they are the outer wings when the wings lay at rest over the body. In stoneflies, they are the top wings when the wings are laid flat over the body. In midges and other true flies, the forewings are the only true wings.
• fork I@t (fork 1@t) - A fork in in the radial sector of many caddisfly wings formed by the branching of veins R₂ and R₃.
• fork II@t (fork 2@t) - A fork in in the radial sector of many caddisfly wings formed by the branching of veins R₄ and R₅.
• fork III@t (fork 3@t) - A fork in the media of caddisfly wings formed by the branching of veins M₁ and M₂.
• fork IV@t (fork 4@t) - A fork in the media of caddisfly wings formed by the branching of veins M₃ and M₄. Typically, this fork is present in forewings but absent in hind wings.
• fork V@t (fork 5@t) - A fork in the anterior branch Cu₁ of the cubitus of caddisfly wings. Despite the numbering, in hind wings it is usually the fourth actual fork because fork IV is absent.
• fossorial - Burrowing.
• friction disc (friction discs) - Oval-shaped structures formed of fine hairs or gills on the bottom of an insect's body, creating friction or suction to help them cling to rocks.
• frons (frontes) - The uppermost anterior part of the head of an insect, and part of its face.
• frontal shelf (frontal shelves) - An shelf-like extension at the front of the head, commonly referenced in some Heptageniidae mayflies.
• frontoclypeus (frontoclypeul) - The frontoclypeus is the combined frons and clypeus when the suture between them is obsolete.
• fumose (fumeus) - Smoke-colored.
• furcal pit (furcal pits) - Small, sharp depressions where the sternum of a stonefly seems to fold into itself, which might colloquially appear like an "armpit" of the insect, although it is not located immediately at the leg joint.
• furcasternum (furcasternal, furcasternite) - The primary, central plate in the posterior portion of an abdominal sternum.
• furcula (furculae) - A forked process. The term is typically used in reference to specific structures, which vary in location and composition across different types of insects.
• furrow (furrows) - A groove in a body part.
• furrow vein (furrow veins) - A wing vein which is concave in the dorsal view with respect to the fluting of the wing, denoted (–).
• fuscous - Brownish gray.
• galea (galeae) - The outer lobe of the maxilla, usually two-jointed, often hoodlike, subject to great modifications.
• galea-lacinia - Combined term for the two lobes of the maxilla, including the outer galea and inner lacinia.
• ganglion (ganglia, ganglionic) - A ganglion is a nerve center composed of a cell mass and fibers. The term is usually found in references to ganglia of the central nerve cord, just inside the ventral surface of the abdomen, which send out nerves to the muscles. They may vary in number and pigmentation in ways that are useful for species identification, especially in mayflies.
• geminate - Arranged in pairs composed of 2 similar or identical parts; i.e. twin structures.
• gena (genae, genal) - An insect's cheek; the side of its face.
• genitalic - Pertaining to the genitals of an insect.
• glabrous - Smooth; devoid of hairs or coarse texture.
• globose - Round-shaped, like a globe.
• glossa (glossae) - The inner pair of lobes at the apex of the prementum in an insect's mouth.
• habitus - The physical and constitutional characteristics of an individual. Typically used meaning a view of the entire insect in an illustration or photo.
• half-spent - The wing position of some insects which fall on the water after mating. Their wings on one side lay flat in the surface film while the wings on the other side stick up into the air. The term may refer to insects with their wings in that position, as well as the position itself. Many mayfly spinners fall half-spent before becoming spent.
• haltere (halteres) - Flies of order Diptera have stubby club-like appendages called halteres in place of hind wings.
• hammer (hammers) - A smooth clearly defined chitinous area on the ventral surface of the ninth abdominal segment of some male stoneflies used for drumming up mates.
• hemitergites (hemiterga, hemitergite, hemitergal) - Divided halves of abdominal tergum IX or X in some adult insects.
• hind wing (hind wings, hindwing, hindwings) - The rear pair of wings of an insect, which are attached to the metothorax, the same thoracic segment that bears the hind legs. In mayflies, the hind wings are much smaller than forewings, and in rare cases absent. In caddisflies, they are the inner wings, covered by the fore wings, when the wings lay at rest over the body. In stoneflies, they are the bottom wings, covered by the fore wings, when the wings are laid flat over the body. Midges and other true flies do not have true hind wings.
• Holarctic - The Holarctic is the biogeographic realm that includes most of the northern hemisphere, including both the Nearctic and Palearctic zoogeographic regions. The term "holarctic" is often used to describe northern species with circumpolar distributions spanning Europe, Asia, and North America.
• holoptic - Having compound eyes that meet along the median dorsal line of the head, with no space between them.
• humeral - Located near the "shoulder" in general, often used to describe wing features located toward the wing base.
• hyaline - Highly transparent, or glassy; usually refers to insect wings, especially those of mayfly spinners.
• hydrofuge - Able to shed water. Mayfly duns have hydrofuge bodies because of tiny hair-like and other structures which help trap air and shed water.
• hypogynial valve (hypogynial valves) - In female Diptera, appendages of abdominal sternum VIII that help guide eggs during ovipositing.
• imago (imagoes) - The sexually mature adult stage of the mayfly is called the imago by scientists and the spinner by anglers.
• immaculate - In descriptions of insect anatomy and coloration, "immaculate" refers to structures lacking any obvious markings.
• incisor (incisors) - A tooth adapted for cutting rather than grinding.
• incurved (incurving) - Curved toward the mid-line of the body.
• infuscated (infouscated) - Tinged with brown.
• instar (instars) - Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.
• integument - The entire outer covering of the body.
• intercalary - Located in the space between major features, most often used in reference to intercalary veins, but may refer to other features, such as the position of hairs or bristles in between segment joints on a stonefly abdomen.
• intercalary bristle (intercalary bristles) - Stout, stubby setae located on the surface of the abdominal tergites of some stoneflies.
• intercalary medius anterior@e (vein IMA@e, IMA vein@e, IMA@e) - An intercalary vein located between the branches of the medius anterior. It is a ridge vein (+).
• intercalary medius posterior@e (vein IMP@e, IMP vein@e, IMP@e) - An intercalary vein located between the branches of the media posterior. It is a ridge vein (+).
• intercalary seta (intercalary setae) - Fine setae located on the surface of the abdominal tergites of some stoneflies.
• intercalary vein (intercalary veins, intercalaries) - Intercalary wing veins are supplemental longitudinal veins in the space between the major veins. They touch the outer margin of an insect's wing but typically do not connect at their base (toward the body) to any other vein, except sometimes via a crossvein.
• intercubital crossvein@p (intercubital crossveins@p, inter-cubital crossvein@p, inter-cubital crossveins@p.) - Intercubital crossveins are crossveins that connect the branches of the cubitus.
• interpenial cleft - The gap between the two lobes of the penes in insects.
• intrasegmental - Located in between the segments.
• irrorate - Marked with small, scattered spots or marks
• keel - Sometimes used in insect anatomy to describe a ridge shaped like the keel of a boat.
• labial palp (labial palpae, labial palps, labial palpal, labial palpus, labial palpi) - A segmented sensory appendage attached to the labium in an insect's mouth.
• labium (labial) - The lower mouth parts of an insect; the lower lip.
• labral fan (labral fans) - Paired, stalked, fanlike structures arising laterally from labrum on the head of black fly larvae (Simuliidae).
• labrum - The platelike structure forming the roof of the mouth of insects; the upper lip.
• lacinia (laciniae, lacinial) - The inner lobe of the maxilla, articulated to the stipes and bearing brushes of hairs or spines.
• lamella (lamellae) - An individual plate-like or leaf-like body part, such as those forming all or part of the gills of many mayflies.
• lamelliform - Insect gills which are flat and platelike are described as lamelliform.
• lanceolate - Long and pointy, like the tip of a spear or lance.
• larva@ (larvae@, larval@) - Many classes of aquatic insects, such as caddisflies, midges, craneflies, dobsonflies, alderflies, and many more, are known as "larvae" rather than "nymphs" in their juvenile stages. They have mostly soft bodies rather than hard exoskeletons. These insects also advance through a "pupa" stage before reaching adulthood.
• lateral (laterally, laterad) - A lateral position is located to the side of a body or structure, as viewed from the top.
• lateral stylet (lateral stylets) - Accessory, lateral, sclerotic processes of the supraanal lobe in stoneflies.
• leaf drift - The mass of dead leaves gathered on the bottom of the stream, sometimes stacked thick in still places like back eddies. Many aquatic invertebrates use the leaf drift for shelter and food. Most insects shred the leaves to digest the bacteria and plankton living on them, rather than digesting the leaves themselves.
• life history (life histories) - The detailed life cycle of an organism, including the stages it passes through and characteristic behavior relating to growth and reproduction.
• lobate - Having lobes.
• longitudinal (longitudinally) - A longitudinal structure is aligned with the axis from the front to the back of a body or structure.
• longitudinal vein (longitudinal veins, longitudinals) - Longitudinal veins are the major long veins running length-wise through an insect's wing, connecting the base to the outer margin, or the major branches from those veins.
• lunate - Shaped like a crescent moon.
• macropterous (macroptery) - Having long (i.e., normal-length) wings, in contrast to brachypterous.
• macula (maculate, maculae, maculation) - Maculae are relatively large, distinct spots or blotches on the surface of an insect's body or wing.
• madder - A deep red color.
• madicolous - Inhabiting a thin film or sheet of water.
• mandible (mandibles, mandibular) - The paired jaws of an insect which are used for grabbing food, located immediately behind the labrum.
• margining (marginings) - Coloration along the edge of a structure.
• marl - Loose sand, silt, or clay containing a high concentration of calcium carbonate.
• masking hatch (masking hatches) - When two types of insects are on the water simultaneously and the trout are feeding on the less noticeable one, the more prominent insect (usually brighter and/or larger but less abundant) is known as a masking hatch.
• maxilla (maxillae, maxillary) - A set of paired mouth parts located behind the mandibles in most arthropods.
• maxillary palp (maxillary palpae, maxillary palps, maxillary palpal, maxillary palpus, maxillary palpi) - The maxillary palp is a segmented (one to seven segments) sensory appendage attached to the maxilla of an insect's mouth.
• media@e (vein M@e, M vein@e, M@e) - The media (denoted M) is the fourth major longitudinal wing vein in insects, located behind the radial sector. In mayflies, its forks MA and MP often appear to be two separate longitudinal veins throughout.
• media@p (vein M@p, M vein@p, M@p, M_1@p, M_2@p, M_3@p, M_4@p, M_1+2@p, M_3+4@p, vein M_1@p, vein M_2@p, vein M_3@p, vein M_4@p, vein M_1+2@p, vein M_3+4@p, M_1 vein@p, M_2 vein@p, M_3 vein@p, M_4 vein@p, M_1+2 vein@p, M_3+4 vein@p) - The media (denoted M) is the fourth major longitudinal wing vein in insects, located behind the radial sector. It can split into up to four branches denoted M_{1 through M4 from front to back. Smaller number of branches may be numbered as combinations of these potential branches, such as M3+4.}
• media@t (vein M@t, M vein@t, M@t, M_1@t, vein M_1@t, M_1 vein@t, M_2@t, vein M_2@t, M_2 vein@t, M_3@t, vein M_3@t, M_3 vein@t, M_4@t, vein M_4@t, M_4 vein@t, M_1+2@t, vein M_1+2@t, M_1+2 vein@t, M_3+4@t, vein M_3+4@t, M_3+4 vein@t, vein MA@t, MA vein@t, MA@t, vein) - The media (denoted M) is the fourth major longitudinal wing vein in insects, located behind the radial sector. In caddisflies, it splits into anterior branch MA (sometimes called M₁₊₂) and posterior branch MP (sometimes called M₃₊₄). In both wings, MA splits into an anterior branch M₁ and posterior branch M₂. In caddisfly forewings, MP typically splits into M₃ and M₄, but it does not split in hind wings.
• medial - Toward the middle of the body.
• medial cell@t (mc@t, cell mc@t, mc cell@t) - The medial cell (denoted mc) in many caddisfly wings is formed by the branching of the media into MA and MP and closed apically by the medial crossvein.
• medial crossvein@t (m@t, crossvein m@t m crossvein@t) - In caddisfly wings, the medial crossvein (denoted m) connects the anterior branch MA and posterior branch MP of the media and forms the apical edge of the medial cell.
• median (medial, medially, mesal, mesally) - In, at, or pertaining to the middle of a body or body part.
• median vein (median veins) - Longitudinal veins in an insect fore wing in between the radial and cubital veins.
• medio-cubital crossvein@p (mediocubital crossvein@p, m-cu crossvein@p, crossvein m-cu@p, m-cu@p) - The medio-cubital crossvein (denoted m-cu) is a crossvein connecting the media to the cubitus@cu, often near the bases of their forks.
• medio-cubital crossvein@t (m-cu crossvein@t, crossvein m-cu@t, m-cu@t) - The medio-cubital crossvein (denoted m-cu) is a crossvein connecting the media to the cubitus@cu, often near the bases of their forks.
• mediodorsal (medio-dorsal, mediodorsally, middorsally, mid-dorsally, medio-dorsally, middorsal) - Located toward the middle of the top of a body or structure.
• medius anterior@e (media anterior@e, vein MA@e, MA vein@e, MA@e, vein MA_1@e, MA_1 vein@e, MA_1@e, vein MA_2@e, MA_2 vein@e, MA_2@e) - Vein MA is the anterior fork of the media, which is the “fourth” major longitudinal wing vein in insects. However, in mayfly forewings, the two forks often appear to be separate veins all the way to the wing base, and MA sometimes appears to branch from Rs near its base. Vein MA itself usually forks into an anterior fork MA₁ and a posterior fork MA₂. Usually, MA can be quickly located in mayfly forewings by looking for the vein that splits the wing in half length-wise and forks in two somewhere around 2/3 of the way from the base to the tip. MA and its forks are ridge veins (+).
• medius posterior@e (media posterior@e, vein MP@e, MP vein@e, MP@e, vein MP_1@e, MP_1 vein@e, MP_1@e, vein MP_2@e, MP_2 vein@e, MP_2@e) - Vein MP is the posterior fork of the media, which is the “fourth” major longitudinal wing vein in insects. However, in mayflies, the two forks often appear to be separate veins all the way to the wing base. Vein MP itself sometimes forks into an anterior fork MP₁ and a posterior fork MP₂, although MP₂ sometimes only indirectly connects to MP via a crossvein. MP and its forks are furrow veins (–).
• membraneous - Made of a membrane. This term is often used to distinguish the kind of soft tissue that makes up the body of a grub from the harder, sclerotized parts that make up the exoskeleton of a nymph, although hard-bodied insects often have small membraneous parts too.
• mentum - The distal division of the postmentum.
• mesepisternum (mesepisternal) - The episternum of the mesothorax.
• mesobasisternum (mesobasisternal) - The basisternum of the mesothorax.
• mesofurcasternum (mesofurcasternal) - The furcasternum of the mesothorax.
• mesomere (mesomeres) - In most insects in which the primary phallic lobes of the male reproductive organs are secondarily divided, the lateral divisions are called the parameres and the inner divisions are called the mesomeres; these form the two types of phallomeres.
• meson - The midline of the body.
• mesonotal setal areas (mesonotal setal area, mesonotal (sa)1, mesonotal (sa)2, mesonotal (sa)3) - Setae on the mesonotum of caddisfly larvae arise mostly from three primary locations, denoted sa1, sa2, and sa3. These differ from the more commonly-referenced metanotal setal areas in that they do not necessarily appear on raised bumps. Often, the entire mesonotum is sclerotized, and these areas do not appear different from the rest of it except for the presence of the setae.
• mesonotum (mesonota, mesonotal) - The top of the insect mesothorax.
• mesopleuron (mesopleura, mesopleural) - The side of the insect mesothorax, and the part to which the fore wings are attached in mayflies.
• mesoposterior - Toward the middle of the posterior end of a body or structure.
• mesoscutellum (mesoscutellar) - The scutellum on the mesothorax.
• mesoscutum (mesoscutal) - The scutum of the mesothorax.
• mesosternal Y-arm (mesosternal Y-arms) - A roughly Y-shaped complex of grooves set into the mesosternum of some stoneflies.
• mesosternal Y-stem (mesosternal Y-stems) - The base or bottom part of the 'Y' shape in the mesosternal Y-arms, which in some cases may be a single line that does not actually branch into a 'Y' shape.
• mesosternum (mesosterna, mesosternal) - The bottom of the insect mesothorax, to which the middle pair of legs are attached.
• mesothorax (mesothoracic) - The middle of the three segments of an insect's thorax, to which its middle pair of legs and the forewings (if present) are attached.
• metabasisternum (metabasisternal) - The basisternum of the metathorax.
• metacephalic rod (metacephalic rods) - In some Diptera larvae, an elongate pair of dorsal sclerites within the thorax, representing posterior portion of the head.
• metafurcasternum - The furcasternum of the metathorax.
• metanotal setal warts (metanotal setal wart, metanotal setal areas, metanotal setal areas, metanotal (sa)1, metanotal (sa)2, metanotal (sa)3) - The setal areas or setal warts on the caddisfly larva metanotum are clearly defined, often sclerotized, gently convex bumps that bear numerous setae. Their configuration is useful for identification. There are typically three on each side of the metanotum, denoted sa1 (near the front in the middle of the metanotum), sa2 (closer to the back, but still near the middle), and sa3 (a typically-longer patch near the edge of the metanotum).
• metanotum (metanota, metanotal) - The top of the insect metathorax.
• metapleuron (metapleurons, metapleural) - The side of the insect metathorax, to which the second pair of wings (if any) and the hind legs are attached.
• metapneustic - Having a respiratory system with a single spiracle, located at the posterior end of the abdomen.
• metascutellum (metascutellar) - The scutellum of the metathorax.
• metasternum (metasterna, metasternal) - The bottom of the insect metothorax, to which the hind pair of legs are attached.
• metathorax (metathoracic) - The rear-most of the three segments of an insect's thorax, to which its hind pair of legs and the hind wings (if present) are attached.
• microdrag - The imperceptibly small unnatural motions of an artificial fly on the water, caused by its connection to the line. A trout's whole life is spent watching things drift naturally, and unnatural movement too subtle for us to detect is obvious to their specialized senses.
• microsetae (microseta, microsetal) - Tiny setae.
• microtrichia - Minute spicules or cuticular hairs on the surface of a structure such as a wing membrane or abdominal plate.
• mid-dorsal - Located longitudinally (length-wise) along the center of the body.
• midtibiae (midtibia) - The tibiae on the middle pair of legs.
• molar (mola) - The ridged or roughened grinding surface of the mandible.
• molt@ (molting@) - When aquatic insects with hard exoskeletons (like mayfly and stonefly nymphs) grow bigger, their exoskeleton does not grow with them. Instead they grow a new, larger one underneath and shed the old one when it's too small. This process is called molting.
• monotypic - a taxonomic level containing a single lower level. Example - a genus consisting of a single species.
• morphology - The form and structure of an organism, or the study of the form and structure of organisms.
• mouth brush (mouth brushes) - In some larval Diptera, ventral, moveable, brushlike organs of the labrum, which strain food particles from the water.
• multibrooded - Producing more than one generation in a single year. Baetis mayflies are a classic example. Insects which produce a single generation with two distinct peaks (like the June and September hatches of Isonychia bicolor mayflies) are not multibrooded, because the fall insects are offspring from the previous fall instead of the current year's spring.
• multivoltine - Having more than one generation per year.
• naiad (naiads) - Naiad is the technical term for nymph used by modern entomologists.
• nasus - A nose-like part of the head, referring sometimes to different structures in different taxa. In some adult craneflies (Tipulidae), it is a small projection on the rostrum.
• natural@ (naturals@) - A natural is a real insect (or similar creature) a trout might eat. The term is used to specify the real thing as opposed to its artificial imitation.
• Nearctic - The zoogeographical region made up of North America, as far south as northern Mexico, and Greenland.
• Neotropical - The zoogeographical region made up of Central and South America, the tropical southern part of Mexico, and the Caribbean.
• neuration - A rarely-used synonym for venation, typically referring to wing veins.
• notum (nota, notal) - The dorsal surface of an insect's thorax or any segment of the thorax.
• nygma (nygma@t) - A small, hardened sensory spot lying within Fork II (near its base) in the wings of most caddisflies.
• nymph@ (nymphs@) - The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).
• oblique (obliquely) - Slanting; neither parallel nor at a right angle.
• obscolescent - In entmology, obsolescent structures are those in the process of disappearing or of becoming nonfunctional.
• obsolescent - Becoming obsolete; may be used in reference to anatomical features or markings that are becoming faded or otherwise difficult to see.
• occipital foramen - The opening at the back of the head through which the alimentary canal, nerve cord, and some
  muscles pass.
• occipital ridge (occipital ridges) - An elevated plate or seam at the back of the head. Usually concave in shape with a row of spinules (tiny spines) running along it.
• occiput (occipital) - The back of the head.
• ocellar triangle - A triangular area on the head with three ocelli as its corners.
• ocellus (ocelli, ocellar) - A simple non-compound, single lens eye found in many arthropods. Most aquatic insects have two, three, or none, located between the compound eyes on the head. As an adjective, "ocellar" refers to the region near the ocelli.
• ochre (ochreous, ocherous) - A light brownish-yellow color.
• olivaceous - Olive-colored; a light or dark yellowish green.
• ommatidia - The individual parts composing the compound eye.
• operculate (operculum) - Lidlike; usually used to describe the pair of enlarged elytroid gills (called the operculum) which some silt-dwelling mayfly nymphs such as Caenis and Eurylophella have developed to shield their other gills from debris.
• orthorrhaphous - Members of the Diptera suborder Brachycera in which the pupa or adult escapes from the last larval skin through a T-shaped opening in the back.
• outcurved (outcurving) - Curved laterally, or away from the mid-line of the body.
• oviposit (ovipositing) - To lay eggs.
• ovipositor (ovipositors) - A long, sometimes tube-like structure at the rear of female insects which helps them lay their eggs.
• ovoid - Oval-shaped.
• ovum (ova) - Egg.
• Palearctic - The zoogeographical region made up of Eurasia north of the Himalayas, North Africa, and the temperate part of the Arabian peninsula.
• palmate (palmated, palmately) - Broad and flat like the palm of a hand, but usually used in reference to a structure with fingerlike parts branching off of it, like a moose antler.
• palp (palpus, palps, palpi) - A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the palpus.
• papilla (papillae) - A minute, soft projection.
• paragenital plate (paragenital plates) - In male stoneflies, plates located laterally at the base of the supraanal lobe.
• paraglossae (paraglossa) - A paired structure on the labium at the apex of the prementum, lying on each side of the glossae.
• paramere (parameres) - In most insects in which the primary phallic lobes of the male reproductive organs are secondarily divided, the lateral divisions are called the parameres and the inner divisions are called the mesomeres; these form the two types of phallomeres.
• paraproct (paraprocts) - Paired, ventral extensions of the sternite on the last abdominal segment of some aquatic insects. The term is used more broadly to describe various appendages in the anal area of some other insects.
• parthenogenesis - In some species of insects and other living things, such as the mayfly species Ameletus ludens, reproduction can take place without fertilization by a male. This process is called parthenogenesis.
• pectinate (pectinations) - Pectinations are tooth-like spines, arranged in rows like a comb, often found on the tarsal claws of some mayfly nymphs. Structures with pectinations are said to be pectinate.
• pedicel (pedicels) - Typically refers to the second segment of an antenna, but can sometimes refer to a stalk or stem supporting an organ or other structure.
• peg sensilla (peg sensillum) - Minute, stout, peg-shaped sensory organs.
• penciling (pencilings) - Thin markings, as if drawn by a pencil.
• penes - The paired genital structures of most male insects, which vary widely in form and are one of the main characteristics used for species identification.
• penultimate - Second-to-last.
• petiole (petiolate) - A petiole is a stalk, like the one attaching a leaf to the plant stem, and organs extended on a stalk are said to be petiolate. This term is also used to describe forks in wing veins that appear at the end of a single vein (like a letter Y) instead of splitting immediately (like a V).
• phallicata - In male insects, the distal sclerotized portion of a divided phallus.
• phallomere (phallomeres) - In most insects in which the primary phallic lobes of the male reproductive organs are secondarily divided, the divisions are called phallomeres, and they consist of lateral divisions called parameres and median divisions called mesomeres.
• pharate adult (pharate adults) - Caddisflies are considered to be pupae during their transformation from larva into adult. This transformation is complete before they're ready to emerge. The emerging insect we imitate with the "pupa" patterns we tie is technically called a pharate adult. It is a fully-formed adult caddisfly with one extra layer of exoskeleton surrounding it and restricting its wings.
• pharyngeal skeleton - In some larval Diptera, a conspicuous sclerotic structure lying in the anterior end of the body.
• phylogeny (phylogenies) - The evolutionary history and development of a taxon.
• piceous - Pitch black.
• piscivorous (piscivore) - Anything which eats primarily fish is a piscivore.
• planate - Shaped with a straight edge or a flat surface.
• planta (plantar) - The sole of the foot.
• pleural fold (pleural folds) - The junction along the sides of an insect's abdomen where the tergites meet the sternites.
• pleuron (pleura, pleural) - The side of the thorax of an adult insect.
• plumbeous - The shade of gray matching the color of lead.
• plumose - Having many fine filaments or branches, creating a feathery appearance.
• polar cap (polar caps) - Coverings of additional material at at one or two poles of an insect egg (imagine the polar ice caps, if Earth were an egg).
• posterior (posteriorly, posterad) - Toward the back of an organism's body. The phrase "posterior to" means "in back of."
• posterolateral (posterolaterally, postero-lateral, postero-laterally) - Located to the side along the posterior (back) end of a body or structure.
• posteromesal (posteromesally, posteromedial, posteromedially, postero-mesal, postero-mesally, postero-medial, postero-medially) - Located in the middle on the lateral axis, but toward the posterior end of a body or structure.
• posteroventral (posteroventrally) - Toward the bottom and back of a body or structure.
• postfurcal (postfurcal) - Located posterior to the furcasternum.
• postfurcasterum (postfurcasternal) - A plate posterior to the furcasternum.
• postmentum - The basal part of the labium, divided into a proximal submentum and distal mentum.
• postnotum (postnotal, postnota) - In adult Diptera, the dorsal sclerite below and behind the scutellum of the mesothorax.
• postocular - Located behind the eyes.
• pre-apical - Located somewhere before the apex of a structure, often used for adult caddisflies to describe tibial spurs located toward the middle of the tibia as compared to the apical spurs.
• preapical - Located just before the apex.
• prehensile - Fitted or adapted for grasping, holding or seizing.
• presternum (presternal) - A a narrow anterior area of the sternum sometimes set off from the basisternum by a submarginal suture of the eusternum.
• pretarsus (pretarsal) - The last segment of the insect leg, being either a single-claw segment or a pair of claws, arolium and auxillae.
• proboscis - An extension various mouth parts of an insect into a long, thin structure, such as the apparent "tongue" of a butterfly or moth.
• procoxae (procoxa, procoxal) - The coxae on the forelegs.
• proleg (prolegs) - Any process or appendage that serves the purpose of a leg but does not have the exact structure and evolutionary origin of an actual leg.
• pronotum (pronotal, pronota) - The top of the insect prothorax.
• propleuron (propleura, propleural) - The side of the insect prothorax.
• propneustic - Having a respiratory system with a single spiracle located on the mesothorax.
• prosctheca (proscthecae) - A mandibular sclerite set with hair, attached with articulation to the basalis, and equivalent to the lacinia of the maxilla
• prosternal horn (prosternal horns) - A membranous, horn-shaped projection of the prosternum of some larval caddisflies.
• prosternum (prosternal) - The bottom of the insect prothorax.
• prothorax (prothoracic) - The frontmost of the three segments of an insect's thorax, to which its front pair of legs are attached.
• proximal (proximad, proximally) - Close to the base or point of origin; for example, on a leg or wing, the proximal parts are those closest to the body.
• pterostigma - A pigmented cell or group of cells found on the wing of some insects, typically located near the wing's leading edge. It is often larger and more heavily pigmented than the surrounding cells.
• ptilinal suture (ptilinal sutures) - A transverse groove that crosses just above the antennae and extends down laterally, in the form of an inverted U, toward the clypeus.
• pubescent (pubescence) - Clothed with soft, short, fine, loosely set hair.
• pulvilliform - Lobe-like or pad-like.
• punctate (punctated) - Studded with tiny dots or holes.
• pupa@ (pupae@) - Any insect which spends most of its juvenile lifetime as a larva first becomes a pupa for a time before emerging as a fully grown adult. Depending on the species, the pupal form can be very important for fly fishermen to imitate.
• quadrate - Approximately square or rectangular, although edges and corners may be slightly rounded.
• radial crossvein@t (crossvein r@t) - The radial crossvein (denoted r) connects the main branch of the radius R₁ to the radial sector Rs near the discoidal cell in some caddisflies.
• radial sector@e (vein Rs@e, Rs vein@e, Rs@e) - The radial sector (denoted Rs) is a group of longitudinal wing veins that normally branch posteriorly off the radius, but in mayflies usually appears detached at the base, looking like a separate vein rather than a branch. In some mayflies, especially in hind wings, it may even branch off of vein MA instead. It may have up to four branches (denoted R₂ through R₅) reaching the wingtip, with intercalaries in between. Vein Rs and all its attached branches are furrow veins (–), but their intercalaries can be ridge veins.
• radial sector@p (vein Rs@p, Rs vein@p, Rs@p) - The radial sector (denoted Rs) is group of longitudinal wing vein branches that arise posteriorly from the radius. It may have up to four main branches (denoted R₂ through R₅) reaching the wingtip, some of which can branch more finely themselves.
• radial sector@t (vein Rs@t, Rs vein@t, Rs@t, R_2@t, vein R_2@t, R_2 vein@t, R_3@t, vein R_3@t, R_3 vein@t, R_4@t, vein R_4@t, R_4 vein@t, R_5@t, vein R_5@t, R_5 vein@t, R_2+3@t, vein R_2+3@t, R_2+3 vein@t, R_4+5@t, vein R_4+5@t, R_4+5 vein@t) - The radial sector (denoted Rs) is group of longitudinal wing vein branches that arise posteriorly from the radius. In caddisflies, vein Rs divides into two branches (R₂₊₃ and R₄₊₅), which both split again, forming four total branches R₂ through R₅.
• radial space (radial space@e) - In mayfly wings, the radial space refers to the area in between the radius and the radial sector.
• radial vein (radial veins) - Major longitudinal veins on the insect fore wing in between the subcostal and median veins.
• radio-medial crossvein@p (radiomedial crossvein@p, r-m crossvein@p, crossvein r-m@p, r-m@p) - The radio-medial crossvein (denoted r-m) is a crossvein connecting the radial sector to the media, often near the bases of their forks.
• radio-medial crossvein@t (r-m crossvein@t, crossvein r-m@t, r-m@t) - The radio-medial crossvein (denoted r-m) is a crossvein connecting the radial sector to the media, often near the bases of their forks.
• radius@e (radial@e, first radial vein@e, vein R_1@e, R_1 vein@e, R_1@e, vein R@e, R vein@e, R@e) - The radius (with its main branch denoted R₁) is the third major longitudinal wing vein, located behind the subcosta. In mayfly forewings, it usually extends to a point near the wingtip. It is a ridge vein (+).
• radius@p (radial@p, first radial vein@p, vein R_1@p, R_1 vein@p, R_1@p, R@p, vein R@p, R vein@p) - The radius (denoted R) is the third major longitudinal wing vein in insects. In stoneflies, its principal branch R₁ is often the strongest, thickest vein, running parallel to the front wing edge for most of its length and appearing to be the second vein in places where the subcosta does not reach.
• radius@t (radial@t, first radial vein@t, vein R_1@t, R_1 vein@t, R_1@t, R@t, vein R@t, R vein@t) - The radius (denoted R) is the third major longitudinal wing vein in insects. In caddisflies, its principal branch R₁ runs nearly parallel to the front wing edge for most of its length and may be very close to the subcosta.
• reticulation (reticulations, reticulate) - A reticulation is a pattern of fine, interlacing markings resembling a net mesh, and structures marked with this pattern are reticulate.
• retractile - Capable of being produced and drawn back or retracted.
• ridge vein (ridge veins) - A wing vein which is convex in the dorsal view with respect to the fluting of the wing, denoted (+).
• rostrum (rostral, rostra) - A snoutlike projection or rigid extension of the head, bearing the mouthparts at the end.
• sagittate - Elongated and triangular; shaped like the head of an arrow.
• scape (scapes) - The first or basal segment of an antenna.
• sclerite (sclerites, sclerotized, sclerous, sclerotic) - An individual sclerite is a single, uninterrupted, hard plate of chitinous material, such as those that form the exoskeletons of arthropods. Structures are said to be sclerotized or sclerous if they are fully or partially covered by sclerites.
• scutellum (scutellar) - The posterior division of the notum of the mesothorax and metathorax.
• scutum - The middle, often largest division of the notum on the mesothorax and metathorax.
• searching pattern (searching patterns) - Any artificial fly pattern used when trout that aren't feeding selectively on anything in particular. A searching pattern may be an attractor or an imitation of something specific that the fish might favor even though it's not currently hatching.
• second radial vein@e (vein R_2@e, R_2 vein@e, R_2@e) - The second radial vein (denoted R₂) is the anterior branch of the radial sector. It is a furrow vein (–).
• sectorial crossvein@t (s@t, crossvein s@t, s crossvein@t) - The sectorial crossvein (denoted s) in caddisflies connects the main forks of the radial sector (typically connecting R₃ to R₄) to form the discoidal cell.
• semilunar - Shaped like a half-moon or crescent.
• semioperculate - In contrast to operculate gills, which cover subsequent gills in a lid-like fashion, semioperculate gills provide only partial coverage.
• sensilla basiconicum (sensilla basiconica) - A thin-walled peg sensillum with minute pores, functioning in chemoreception.
• sessile - Directly attached without a stem or petiole. For example, when speaking of a fork in a wing vein, a sessile fork is one that branches directly from some other vein as a fork (like in a V shape) rather than extending on a separate stem that forks in two (like a Y shape).
• seta (setae, setiferous, setose, setaceous, setal, setation) - Setae are usually small hairs on insects, although the term can sometimes refer to thicker, scaly structures of similar origin and configuration.
• setal wart (setal warts) - A setiferous wart on the dorsum of the head or thorax of adult caddisflies.
• shuck (shucks) - The shed exoskeleton left over when an insect molts into its next stage or instar. Most often it describes the last nymphal or pupal skin exited during emergence into a winged adult.
• sinuate (sinuous, sinusoidal, sinuately) - Having a smooth, wavy shape, like a sine wave.
• somite (somites) - An abdominal segment.
• spatulate - Broadly flattened, like a spatula.
• spent@ - The splayed-out wing position of mayflies and other insects when they fall dead on the water after mating.
• spermatheca (spermathecal) - In female insects, receptacle of the sperm during mating.
• spiculate - Having numerous spines.
• spicule (spicules) - Small, needle-like spines.
• spinasternum (spinasternum) - One of the spina-bearing intersegmental sclerites of the thoracic venter, associated, or united, with the preceding sternum.
• spiniform - Spine-shaped.
• spinner@ (spinners@) - There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.
• spinose (spinuous, spiniferous, spined) - Spinose structures have spines attached, whether just a few or a full covering of spines.
• spinule (spinula, spinulae, spinules) - A small spine.
• spiracle (spiracles, spiracular) - An external tracheal opening through which some arthropods breathe.
• spiracular plate (spiracular plates) - In larval Diptera, a fairly well-defined plate on which the spiracular opening and ecdysial scar are located.
• spuraanal - Located above the anus.
• stemmata - Small tubercles on antennae.
• sternacostal suture (sternacostal sutures) - The transverse division of an abdominal sternum separating the basisternum in the anterior part from the furcasternum in the posterior part.
• sternellum - The second sclerite of the ventral part of each thoracic segment.
• sternite (sternites) - The bottom (ventral) part of a single segment on an insect's abdomen.
• sternum (sterna, sternal) - The entire ventral (bottom) division of any part of an insect's body.
• stigma (stigmatic) - A small mark, spot, or pore on an animal or organ, sometimes used in relation to spiracles.
• stigma@t (pterostigma@t, stigmatic@t) - In caddisflies, the stigma (or pterostigma) is a sometimes thickened or darkly marked region along the anterior edge of the forewing between the apices of the subcosta and radius.
• stigmatic area - The stigmatic area is the part of an insect's fore wing near the tip of the front edge. Its characteristics are often important for identification.
• stillborn (stillborns) - In fly fishing, a stillborn insect is one which got stuck in its nymphal or pupal shuck during emergence and floats helplessly on the surface instead of flying away. It is a specific class of cripple, although it is sometimes used interchangeably with that term.
• stipes - The large central sclerite of the maxilla.
• stria (striae) - Any fine, longitudinal impressed line.
• stylus (styli, stylet, stylets) - A pointed, stiff process that is not articulated or jointed. May also be called a style. A particularly small style is a stylet.
• subanal plate (subanal plates) - A distinct plate-like structure near the posterior end of an insect's abdomen, this term can mean different things (i.e. parts of different abdominal segments) for different insects.
• subanal probe (subanal probes) - A structure located at the tip of the abdomen in adult stoneflies, which varies greatly in structure across species and is sometimes useful in identification.
• subannulated - Almost or approximately annulated.
• subapical - Located near, but not quite at, the apex.
• subclavate - Somewhat thickened toward the tip, but not quite club-shaped.
• subcosta@e (subcosta@e, subcostal@e, subcostal vein@e, vein Sc@e, Sc@e vein, Sc@e) - The subcosta (denoted Sc) is the second major longitudinal wing vein, located behind the costa, which it usually closely parallels along the leading edge of a mayfly’s forewing. It is a furrow vein (–).
• subcosta@p (subcostal@p, subcostal vein@p, vein Sc@p, Sc@p) - The subcosta (denoted Sc) second major longitudinal wing vein, located behind the costa. In stoneflies, it often appears to be a short (about 1/3 wing length) loop off of the third vein, the radius.
• subcosta@t (subcostal@t, subcostal vein@t, vein Sc@t, Sc vein@t, Sc@t) - The subcosta (denoted Sc) second major longitudinal wing vein, the first one posterior to the wing edge or costa and anterior to the radius.
• subcylindrical - Almost but not exactly cylindrical.
• subequal - Almost but not exactly equal.
• subgenital plate (subgenital plates) - A plate below the genitalia, which can arise from different structures or take a variety of forms in different taxa. For example, in mayflies, it may be a produced part of sternum VII. In stoneflies, it may refer to a part of sternum IX in males or VIII in females.
• subhyaline (sub-hyaline) - Almost but not completely transparent; just slightly opaque.
• subimago (subimagoes, subimaginal) - Mayfly nymphs emerge from the water into subimagoes, better known to anglers as "duns." They are a sexually immature, winged, recognizably adult stage and they must molt one more time into imagoes or "spinners" before they can mate.
• submarginal - Almost but not quite at the edge or end.
• submedial (submedially) - Slightly below or to the side of the mid-line of a body or structure.
• submedian - Located near but not quite in the middle of a body or structure.
• submentum (submental) - The basal division of the postmentum.
• suboccipital - Situated under, or posterior to, the occiput.
• subopaque - Almost but not entirely opaque; just slightly transparent.
• subparallel - Almost or approximately parallel.
• subquadrate - Almost or approximately rectangular, but with some slight rounding of the corners or curvature of the sides.
• subrectangular - Almost or approximately rectangular.
• subsessile - Almost but not entirely sessile.
• subtriangular - Almost but not quite triangular, being somewhat rounded at the corners or curved on the edges instead.
• subtruncate - Almost but not completely cut-off or truncated.
• suctorial - Adapted for sucking.
• suture (sutures) - A groove marking the line of fusion of two formerly distinct plates of an arthropod's exoskeleton.
• synonym (synonyms) - The former name of a taxon, usually a species. Entomologists frequently discover that two insects originally described as different species are actually the same, and they drop one of the names. The dropped name is said to be a synonym of the remaining name.
• synthorax (pterothorax) - The synthorax or pterothorax refers to the mesothorax and metathorax together when they are closely fused to each other.
• tarsal claw (tarsal claws) - The claws at the tip of the tarsus, on an insect's "foot."
• tarsus (tarsi, tarsal) - The often multi-segmented outer leg section of an insect, which attached to the tibia. Colloquially, it's the closest thing an insect has to a "foot."
• tentorium (tentoria, tentorial) - The endoskeleton of the head, serving as a brace and site for attachment of muscles.
• tergite (tergites) - The top (dorsal) part of a single segment on an insect's abdomen when it consists of a single chitinous plate (sclerite), or an individual sclerite if the segment has more than one.
• tergum (terga, tergal) - The dorsal part of an abdominal segment. Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.
• terminal filament (terminal filaments) - The technical term for the middle tail of a 3-tailed insect (the outer tails being called cerci).
• terminal segment (terminal segments) - The outermost part of a segmented structure, i.e. the segment forming its tip.
• terrestrial (terrestrials) - Insects which live on land and are fed on by trout only when they incidentally fall into the water are known as "terrestrials" to fly anglers, and they're very important in late summer.
• testaceous - Brownish-yellow.
• the drift (the invertebrate drift) - The invertebrate drift refers to all the invertebrates suspended in the water column, or on the surface, of a river, being transported downstream by the current. It includes aquatic and terrestrial insects, drifting on purpose or by accident, and it is the primary food source for most trout.
• third radial vein@e (vein R_3@e, R_3 vein@e, R_3@e) - The third radial vein (denoted R₃) is the middle branch of the radial sector. It is sometimes unattached to the base of rs, making it difficult to distinguish from intercalaries except by looking at the fluting. It is a furrow vein (–).
• thorax (thoracic) - The thorax is the middle part of an insect's body, in between the abdomen and the head, and to which the legs and wings are attached.
• thyridial cell@t (tc@t, cell tc@t, tc cell@t) - The thyridial cell (denoted tc) is cell in caddisfly wings formed by the fork between MP@t and Cu₁ being closed apically by the medio-cubital crossvein. It is especially distinctive in the forewings and frequently used as an identifying characteristic.
• thyridium (thyridium@t) - A small, hardened sensory spot lying within the thyridial cell of the wings of some caddisfly species, similar to the nygma but in a different location.
• tibia (tibiae, tibial) - A middle segment in the leg of an insect and usually one of the two longest, located between the femur and the tarsus.
• tibial spur (tibial spurs) - One of a small number of spurs (long, thick spikes) sticking out from the tibia distinctly further than the more numerous, smaller spikes or setae. The number of tibial spurs is often used an identifying characteristic for adult caddisflies, expressed as a list such as 1, 2, 2 denoting the number of spurs on the tibiae of the foreleg, middle leg, and hind leg, respectively.
• titillator (titillators) - Spines, small plates, or slender processes at distal extremity of aedeagus or penes of an insect.
• trachea (tracheae, tracheal, tracheated) - Tracheae are internal air tubes, like those in the gills or the spiracles of an insect's respiratory system. Structures containing tracheae may be described as tracheal.
• transverse (transversely) - Situated or extending across something from side to side, as opposed to longitudinally.
• trifid - Split into three.
• trivoltine - Producing three generations per year.
• trochanter (trochanters) - A short segment near the base of an insect's leg, which joins the coxa on the inside to the femur on the outside.
• trochantin - The trochantin, not to be confused with trochanter, is a plate around the base of the leg in many insects. In caddisfly larva, it seems to be a part of the coxa that often (at least on the foreleg) projects forward in a shape that can be useful for identification. These projections create the appearance of the larva wearing spiky pauldrons (shoulder armor).
• truncate - Cut-off. This is often used to describe the square appearance of the gills of Maccaffertium mayfly nymphs, for example, as opposed to the pointed gills of the closely related genus Stenacron.
• tubercle (tubercles) - Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.
• turbinate - Shaped like a top or elevated on a stalk; usually refers to the eyes of some adult male Baetidae mayflies which are wider near the tip than at the base.
• unidentate - Having one tooth.
• univoltine - Producing only a single generation per year.
• unsclerotized - Not sclerotized.
• vein R_4+5@e (R_4+5 vein@e, R_4+5@e) - The fourth radial vein in mayflies (denoted R₄₊₅) is the posterior branch of the radial sector. Generic insect veins R₄ and R₅ are combined into a single vein R₄₊₅ in mayfly forewings and often in hindwings. It is a furrow vein (–).
• veinlet (veinlets) - Short insect wing veins connecting the major longitudinal veins to the wing margin.
• venation - The pattern in which the veins on the wings of an insect are arranged. It is usually one of the most useful identifying characteristics.
• ventral (ventrally, venter) - Toward or on the bottom.
• ventroapical - Located on the ventral side of a structure near its apex.
• ventrolateral (ventrolaterally) - Located to the side of the lower part of a body or structure.
• ventromesal - Toward the middle bottom of a body or structure.
• vertex (vertices) - In entomology, vertex refers to the top of an insect's head.
• vesicle (vesicles) - A small, fluid- or air-filled sac or cyst in the body.
• vestigial (vestige, vestiges) - An anatomical structure which has become dysfunctional or reduced after hundreds of generations of non-use is vestigial, and whatever remains of it is a vestige. The human tailbone is a classic example.
• villopore (villopores) - A ventral patch of fine hairs on the femora of many Baetid mayfly nymphs, which can be very difficult to see, even under a microscope.
• vitta (vitae) - A broad longitudinal stripe.
• viz. - In other words.
• whorl (whorls) - A pattern of spirals or concentric circles, or structures arranged in this pattern.
• wing articulation (wing articulations) - The point at which a wing joins the body.
• wing pad (wing pads) - A protrusion from the thorax of an insect nymph which holds the developing wings. Black wing pads usually indicate that the nymph is nearly ready to emerge into an adult.
• wing root (wing roots, root of fore wing, root of hind wing, root of forewing) - The base of an insect's wing.
• zoogeographical (zoogeographic) - Zoogeographicals regions are large (continent-scale or larger) geographic regions within which animal communities are more similar and closely related than they are among different regions.