Identification: Key to Orders of Aquatic Insect Larvae and Wingless Adults, Couplet 10

Identification: Key to Orders of Aquatic Insect Larvae and Wingless Adults, Couplet 10

• Couplet 10
• Full Key at a Glance

Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)

Option 1	Option 2
Body often 5 mm or larger, elongate, somewhat cylindrical, spindle-shaped or maggot-like	Body usually 5 mm or less
Mouthparts may be reduced to a pair of retractile mouth hooks that move vertically	Mouthparts may be reduced to a pair of opposable, acute mandibles that move horizontally
	Parasitoids on or inside insect hosts
5 Example Specimens Simuliidae (Black Fly) True Fly LarvaSimuliidae (Black Fly) True Fly Larva 4 Pictures Chironomidae (Midge) True Fly LarvaChironomidae (Midge) True Fly Larva 6 Pictures Chironomidae (Midge) True Fly LarvaChironomidae (Midge) True Fly Larva 5 Pictures Chironomidae (Midge) True Fly LarvaChironomidae (Midge) True Fly Larva I don't see a lot of green Chironomidae larvae in my samples, so I photographed this one. 8 Pictures Ptychopteridae (Phantom Crane Fly) True Fly LarvaPtychopteridae (Phantom Crane Fly) True Fly Larva 7 Pictures Previous Next
Diptera	Hymenoptera

Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)

The current couplet is highlighted with darker colors and a icon, and couplets leading to this point have a icon.

Couplet 1

Couplet 1

Leads to Collembola:

• Abdomen with 6 or fewer segments and a ventral tube
• Body tiny, 5 mm or less
• Most with a forked structure (furcula) at tip of abdomen

Collembola

Leads to Couplet 2:

• Abdomen with more than 6 segments and without a ventral tube
• Body size variable, often > 5 mm

Couplet 2

Couplet 2

Couplet 2

Leads to Couplet 3:

• Three pairs of jointed legs on thorax

Couplet 3

Leads to Couplet 8:

• True legs absent; fleshy, leg-like protuberances or prolegs may be present on thorax, but fewer than three pairs and not jointed

Couplet 8

Couplet 3

Couplet 3

Leads to Hemiptera:

• Middle and hind legs long and slender, extending considerably beyond the abdomen
• Compound eyes present

Hemiptera

Leads to Couplet 4:

• Legs not longer than abdomen
• Compound eyes absent

Couplet 4

Couplet 4

Couplet 4

Leads to Lepidoptera:

• Abdomen with at least 2 pairs (usually 5 pairs) of ventral, fleshy, leg-like protuberances tipped with tiny hooks (prolegs with crochets)

Lepidoptera

Leads to Couplet 5:

• Abdomen without paired, ventral, leg-like protuberances, or, if present, not tipped with tiny hooks

Couplet 5

Couplet 5

Couplet 5

Leads to Trichoptera:

• Last abdominal segment with lateral appendages bearing sclerotized, hook-like anal claws
• Antennae 1-segmented, inconspicuous
• Gills, if present, seldom confined to lateral margins of body
• Larvae frequently live in cases made of sand grains or bits of plant matter, but some are free-living

Trichoptera

Leads to Couplet 6:

• Last abdominal segment without anal claws
• If anal claws present, antennae have more than 1 segment
• Gills inserted laterally

Couplet 6

Couplet 6

Couplet 6

Leads to Neuroptera:

• Mandibles and maxillae united at each side to form long, straight or slightly recurved, thread-like suctorial tubes
• Laterally inserted, segmented gills folded beneath abdomen
• Small, 10 mm or less Found in or on freshwater sponges

Neuroptera

Leads to Couplet 7:

• Mandibles not united with maxillae into long tubes; if mandibles suctorial, then strongly curved, sickle-shaped
• Gills seldom segmented and not folded beneath abdomen

Couplet 7

Couplet 7

Couplet 7

Leads to Megaloptera:

• Abdomen with 7-8 pairs of lateral filaments or gills, arranged 1 pair on each segment
• Paired terminal anal prolegs each with 2 claws or a single, medial, caudal filament

Megaloptera

Leads to Coleoptera:

• Abdomen usually without lateral gills; if segmental gills present, then (a) only a single terminal anal proleg with 4 claws, otherwise anal hooks absent, or (b) segment 10 with 4 gills, or (c) caudal appendages paired or absent but never single

Coleoptera

Couplet 8

Couplet 8

Leads to Couplet 9:

• Head capsule distinct, partly or entirely hardened, and usually pigmented, but may be deeply withdrawn in prothorax

Couplet 9

Leads to Couplet 10:

• Head capsule absent, not distinct, hardened, or pigmented, often consisting of a few pale rods

Couplet 10

Couplet 9

Couplet 9

Leads to Diptera:

• Posterior end of body with at least one or a combination of gills, hair brushes, a sucker, or breathing tube

Diptera

Leads to Coleoptera:

• Posterior end of body simple or with small processes or isolated hairs, but without gills, brushes, suckers, or breathing tubes

Coleoptera

Couplet 10

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Couplet 10 (You are here)

Leads to Diptera:

• Body often 5 mm or larger, elongate, somewhat cylindrical, spindle-shaped or maggot-like
• Mouthparts may be reduced to a pair of retractile mouth hooks that move vertically

Diptera

Leads to Hymenoptera:

• Body usually 5 mm or less
• Mouthparts may be reduced to a pair of opposable, acute mandibles that move horizontally
• Parasitoids on or inside insect hosts

Hymenoptera

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References