Identification: Key to Orders of Aquatic Insect Larvae and Wingless Adults, Couplet 6

Identification: Key to Orders of Aquatic Insect Larvae and Wingless Adults, Couplet 6

• Couplet 6
• Full Key at a Glance

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

Option 1	Option 2
Mandibles and maxillae united at each side to form long, straight or slightly recurved, thread-like suctorial tubes	Mandibles not united with maxillae into long tubes; if mandibles suctorial, then strongly curved, sickle-shaped
Laterally inserted, segmented gills folded beneath abdomen	Gills seldom segmented and not folded beneath abdomen
Small, 10 mm or less Found in or on freshwater sponges
	Remaining orders: Coleoptera and Megaloptera
	5 Example Specimens Corydalus (Dobsonfly) Hellgrammite LarvaCorydalus (Dobsonfly) Hellgrammite Larva 27 Pictures Lara Riffle Beetle LarvaLara Riffle Beetle Larva 14 Pictures Nigronia serricornis (Fishfly) Hellgrammite LarvaNigronia serricornis (Fishfly) Hellgrammite Larva 12 Pictures Psephenus (Water Penny) Beetle LarvaPsephenus (Water Penny) Beetle Larva 5 Pictures Coleoptera (Beetle) Insect LarvaColeoptera (Beetle) Insect Larva 3 Pictures Previous Next
Neuroptera No further information about this order is available on Troutnut.com at this time.	Go to Couplet 7

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

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Couplet 6 (You are here)

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

Couplet 10

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