Key to Adult Insects - BIOLOGY JUNCTION

Key to Adult Insects

Start at Question 1 and follow the links until you’ve identified your insect

1	Insect has wings?	Go to 2
	Insect wingless or with poorly developed wings	Go to 29

2	One pair of wings	Go to 3
	Two pairs of wings	Go to 7

3	Body grasshopper-like, with enlarged hind legs and pronotum extending back over abdomen	Orthoptera


	Insects not like this	Go to 4

4	Abdomen with ‘tails’	Go to 5
	Abdomen without ‘tails’	Go to 6

5	Insects <5mm long, with relatively lonbg antennae: wing with only one forked vein	Hemiptera

	Larger insects with short antennae and many wing veins: tails long	Ephemeroptera

6	Forewings forming club-shaped halteres	Strepsiptera
	Hind wings forming halteres (may be hidden)	Diptera

7	Forewings hard or leathery	Go to 8
	All wings membranous	Go to 13

8	Forewings horny apart from membranous tip	Hemiptera
	Forewings of uniform texture throughout	Go to 9

9	Forewings (elytra) hard and veinless, meeting in centre line	Go to 10

	Forewings with many veins, overlapping at least a little and often held roofwise over the body	Go to 11

10	Abdomen ending in a pair of forceps : elytra always short	Dermaptera
	Abdomen without forceps: elytra commonly cover whole abdomen	Coleoptera

11	Insects with peircing and sucking beaks	Hemiptera
	Insects with chewing mouthparts: cerci (‘tails’) usually present	Go to 12

12	Hind legs modified for jumping	Orthoptera
	Hind legs not modified for jumping	Dictyoptera

13	Tiny insects covered with white powder	Go to 14
	Insects not like this	Go to 15

14	Wings held flat at rest: mouth-parts adapted for piercing and sucking	Hemiptera
	Wings held roofwise over body at rest: biting mouthparts	Neuroptera

15	Small, slender insects with narrow, hair-fringed wings: often found in flowers	Thysanoptera
	Insects not like this	Go to 16

16	Head extending downwards into a beak	Mecoptera
	No such beak	Go to 17

17	Wings more or less covered scales: coiled proboscis (tongue) usually present	Lepidoptera
	Wings usually transparent although often hairy	Go to 18

18	Wings with a network of veins, including many cross veins	Go to 19
	Wings with relatively few cross veins	Go to 23

19	Abdomen with long terminal threads	Go to 20
	Terminal appendages short or absent	Go to 21

20	Forewings much larger than hind wings: wings held vertically over body at rest: 2 or 3 terminal threads	Ephemeroptera
	Wings more of less equal in size or hind wings larger: wings folded close to body at rest: 2 terminal appendages	Plecoptera

21	Antennae very short: body at least 25mm long	Odonata
	Antennae longer: greater than width of head	Go to 22

22	Tarsi 3-segmented	Plecoptera
	Tarsi 5-segmented	Neuroptera

23	Wings noticeably hairy	Go to 24
	Wings not noticeably hairy	Go to 25

24	All of wings more or less alike: front tarsi swollen	Embioptera
	Hind wings usually broader than forewings: front tarsi not swollen	Trichoptera

25	Tarsi with 4 or 5 segments	Go to 26
	Tarsi with 1 – 3 segments	Go to 27

26	All wings alike	Isoptera
	Hind wings much smaller than forewings	Hymenoptera

27	Hind wings similar to or larger than forewings: abdomen with cerci	Plecoptera
	Hindwings smaller than forewings: no cerci	Go to 28

28	Tiny insects with at least 12 antennal segments	Psocoptera
	Never more than 10 antennal segments: piercing and sucking beak present	Hemiptera

29	Insects with slender, twig like body	Phasmida
	Insects not like this	Go to 30

30	Insects with grasshopper-like body and long back legs	Orthoptera
	Insects not like this	Go to 31

31	Small, soft-bodied insects living on plants, often under protective sheild or scale	Hemiptera
	Insects not like this	Go to 32

32	Minute soil-living insects, <2mm long without antennae	Protura
	Insects not like this	Go to 33

33	Insects with cerci or other abdominal appendages	Go to 34
	Insects with other appendages	Go to 41

34	Abdominal appendages long and conspicious	Go to 35
	Abdominal appendages short or hidden under body	Go to 38

35	Abdominal appendages forming pincers	Go to 36
	Abdominal appendages not forming pincers	Go to 37

36	Tarsi 3-segmented	Dermaptera
	Tarsi 1-segmented	Diplura

37	Abdomen with 3 long terminal appendages	Thysanura
	Abdomen with only 2 terminal appendages	Diplura

38	Tiny jumping insects, head points downwards forming a beak	Mecoptera
	No sign of beak	Go to 39

39	Small or minute insects with a forked springin organ under rear of abdomen: generally found in soilor decaying vegetation	Collembola
	Insects not like this	Go to 40

40	Tarsi usually 4-segmented	Isoptera
	Tarsi 3-segmented: front tarsi swollen	Embioptera

41	Parasites in fur or feathers: insects generally flattened side-to-side or dorso-ventrally	Go to 42
	Insects not parasitic and not usually flattened	Go to 46

42	Jumping insects flattened from side-to-side	Siphonaptera
	Insects flattened dorso-latterally	Go to 43

43	Insects of moderate size: head partly withdrawn into thorax	Go to 44
	Small minute insects: head not withdrawn into thorax	Go to 45

44	Antennae very short: very ‘leggy’ insectswith strong claws well suited to clinging to a host mammal	Diptera
	Antennae long: body somewhat circular, with less prominant legs and claws	Hemiptera

45	Prothorax distinct: biting mouths	Mallophaga
	Thoracic segments fused into one unit: sucking mouths	Anoplura

46	Abdomen with pronounced ‘waist’: antennae often elbowed	Hymenoptera
	No such features	Go to 47

47	Body >5mm long, clothed with flattened hairs and scales: vestigial wings present	Lepidoptera
	Body usually <5mm long, bald or occasionally scaly: vestigial wings rarely present	Go to 48

48	Head a wide or nearly as wide as body: biting mouthparts: insects often found among dried materials	Psocoptera
	Head narrower than body: sucking mouthparts: abdomen often with a pair of tubular outgrowths near hind end: insects found on growing plants	Hemiptera