Key to Orders of Common Larger Adult Insects

Glossary of Terms

1. (a) One or two pairs of well-developed wings present, though often folded along body and inconspicuous Go to Couplet 2
(b) Wings absent, or present only as small pads or scales less than half length of abdomen Go to Couplet 21
2. (a) Only the front pair of wings present Go to Couplet 3
(b) Two pairs of wings present, hindwings may be concealed beneath protective forewings Go to Couplet 4
3. (a) Front wings hard, opaque, forming protective cover over abdomen, not used for flying Order COLEOPTERA
(b) Front wings membranous, not forming covers, used for flying Order DIPTERA
4. (a) Front wings hard and opaque, at rest forming close-fitting covers for the transparent hindwings; front wings with no branching veins except sometimes just at the apex Go to Couplet 5
(b) Front wings either transparent, or with branching veins over most of surface, or not forming close-fitting covers over hindwings Go to Couplet 7
5. (a) Mouthparts forming a cylindrical sucking rostrum beneath head, often folded between the forelegs; palps absent Order HEMIPTERA
(b) Mouthparts not forming a rostrum; palps present on mouthparts Go to Couplet 6
6. (a) Abdomen with prominent, pincer-like forceps at end; front wings much shorter than abdomen Order DERMAPTERA
(b) Abdomen without prominent, movable forceps; front wings usually as long as abdomen Order COLEOPTERA
7. (a) Wings covered with microscopic, overlapping scales which easily rub off; mouthparts forming a coiled, sucking proboscis (sometimes absent) beneath the head Order LEPIDOPTERA
(b) Wings usually bare or hairy; mouthparts not forming a coiled tube Go to Couplet 8
8. (a) Abdomen usually with 3 long, flexible, segmented filaments at its rear end; if with two filaments then front wings much larger in area than hindwings Order EPHEMEROPTERA
(b) Abdomen usually without 3 long segmented filaments; if with 2 filaments (cerci) then front wings not larger than hindwings (a long central ovipositor may be present in some females but it is not segmented as in the filaments of Ephemeroptera) Go to Couplet 9
9. (a) Mouthparts forming a straight, cylindrical rostrum, sometimes concealed between forelegs; palps absent Order HEMIPTERA
(b) Mouthparts not forming a true rostrum, sometimes elongate but then 2 or more palps are present Go to Couplet 10
10. (a) Forewings thicker and more opaque than hindwings and forming a protective cover for them Go to Couplet 11
(b) Both pairs of wings of similar texture Go to Couplet 14
11. (a) Forelegs armed with spines and modified for seizing prey; prothorax very long Order MANTODEA
(b) Forelegs not modified for seizing prey; prothorax usually not long Go to Couplet 12
12. (a) Body long and narrow, stick- or leaf-like in form; hindlegs not modified for jumping Order PHASMATODEA
(b) Body long and narrow, the hindlegs modified for jumping Go to Couplet 13
13. (a) Thorax covering head when insect viewed from above; hindlegs not modified for jumping Order BLATTODEA
(b) Head visible when insect viewed from above; hindlegs with femora enlarged for jumping Order ORTHOPTERA
14. (a) Antennae minute, bristle-like, shorter than the width of an eye and having only 5-8 segments; wings flat, unfolded Order ODONATA
(b) Antennae normal, longer than width of an eye and having more than 8 segments; wings often folded or pleated when at rest Go to Couplet 15
15. (a) Wings with many veins and cross veins forming a close network over much of wing surface; two cerci sometimes present at tip of abdomen Go to Couplet 16
(b) Cross veins few in number; cerci absent Order HYMENOPTERA
16. (a) Wings deciduous, with a fracture line across their base; veins thickened along the leading edge of wing Order ISOPTERA
(b) Wings not deciduous; all wing veins of about equal thickness Go to Couplet 17
17. (a) Two segmented cerci present at tip of abdomen; body and wings never hairy Order PLECOPTERA
(b) Cerci absent, or small and unsegmented; body and/or wings often hairy Go to Couplet 18
18. (a) Mandibles absent; moth-like insects with hairy wings Order TRICHOPTERA
(b) Mandibles present; usually not moth-like Go to Couplet 19
19. (a) Head drawn out into an elongate beak with mouthparts at apex Order MECOPTERA
(b) Head not noticeably beak-like Go to Couplet 20
20. (a) Wing veins forking just before they reach edge of wing Order NEUROPTERA
(b) Wing veins not forking just before they reach the edge of wing Order MEGALOPTERA
21. (a) Abdomen terminating in 3 long segmented filaments Order THYSANURA
(b) Abdomen with none or 2 terminal segmented filaments (a long central ovipositor may be present in some females but it is not segmented) Go to Couplet 22
22. (a) Abdomen terminating in a pair of stout, pincerlike forceps Order DERMAPTERA
(b) Abdomen without terminal forceps Go to Couplet 23
23. (a) Mouthparts forming a cylindrical rostrum beneath the head; palps absent Order HEMIPTERA
(b) Mouthparts not a rostrum; palps present Go to Couplet 24
24. (a) Abdomen constricted to a narrow waist just behind the forebody Order HYMENOPTERA
(b) Abdomen without a narrow waist Go to Couplet 25
25. (a) Prothorax much longer than mesothorax, sometimes concealing the head when viewed from above Go to Couplet 26
(b) Prothorax small, not much longer than mesothorax, never concealing the head Go to Couplet 27
26. (a) Body broad and flattened; hindlegs not modified for jumping Order BLATTODEA
(b) Body more or less cylindrical; hindlegs with enlarged femora for jumping Order ORTHOPTERA
27. (a) Large, elongate, camouflaged stick- or leaf-like insects Order PHASMATODEA
(b) Small ant-like insects; body not markedly elongate, not camouflaged Order ISOPTERA


  • Abdomen – Third major division of the insect body, generally containing reproductive and digestive organs
  • Cerci (singular: cercus) – Paired appendages at the tip of the abdomen of some insects
  • Deciduous – Falling off or detaching at maturity
  • Femora (singular: femur) – Third leg segments of insects with articulated legs
  • Filaments – Slender threads
  • Forceps – Hook or pincer-like appendages on the abdomen
  • Mandibles – Chewing and biting jaws of an insect
  • Mesothorax – Middle segment of the thorax
  • Order – One of the primary classification levels of organisms
  • Ovipositor – Female egg-laying organ
  • Palps (plural: palpi) – Appendages around the mouthparts which form part of the sensory and feeding organs
  • Proboscis – Modified extended mouthparts, mostly used for taking in liquid food
  • Prothorax – Front segment of the thorax
  • Rostrum – Beak-like sucking mouthparts
  • Thorax – Middle division of the body, usually bearing the legs and wings (when present)

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