Insect Key Part 3

David A Kendall BSc PhD
Consulting Entomologist

2 Birchdene Nailsea Bristol BS48 1QD UK
Tel/Fax: 01275 854224
E-Mail: [email protected]

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Insect Identification

Key to the main Orders of Insects - Part 3

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(insect without wings)
32a.	Small soft-bodied insect living on terrestrial plants with the body encased under a protective shield ('scale') or partly covered with white waxy filaments or powder	Hemiptera
32b.	Insect not like this	33

33a.	Thoracic legs absent or enclosed in a membrane preventing any movement	(Larvae and pupae of most Orders of Endopterygota)
33b.	Thoracic legs present and fully functional	34

34a.	Abdomen with false-legs or prolegs (fleshy structures different from and additional to the jointed legs of the thorax); insect caterpillar-like in general appearance	35
34b.	Abdomen without prolegs; insect not caterpillar-like	37

35a.	No more than 5 pairs of prolegs	Larvae of Lepidoptera
35b.	At least 6 pairs of prolegs	36

36a.	Head with a single small eye (ocellus) on each side	Larvae of Hymenoptera
36b.	Head with several small eyes (ocelli) on each side	Larvae of Mecoptera

37a.	Insect living in a terrestrial habitat or on the surface of water (not underwater)	38
37b.	Insect truly aquatic (living underwater)	Part 5 of the Key

38a.	Abdomen with cerci or other terminal appendages (take care not to confuse terminal hairs or bristles with cerci)	39
38b.	Abdomen without such terminal appendages (though may have small appendages on proximal segments or a pair of tubular outgrowths or cornicles near the hind end)	Part 4 of the Key

39a.	Abdomen with 6 segments or fewer; usually with a forked terminal appendage (springing organ) folded under the rear end when not in use	Collembola
39b.	Abdomen with more than 6 segments (usually 8 or more clearly visible); terminal appendages of a different form	40

40a.	Antennae short and often inconspicuous (at most about the same length as the head)	41
40b.	Antennae long and conspicuous (usually much longer than the head)	42

41a.	Tarsi with at least 3 segments (usually 5-segmented)	Phasmida
41b.	Tarsi with fewer than 3 segments (often reduced to single or paired claws on the end of each leg)	Larvae of Coleoptera

42a.	Hind-legs enlarged and modified for jumping; insect grasshopper-like in general appearance	Orthoptera
42b.	Hind-legs not modified for jumping and usually similar in thickness to the middle-legs; insect not grasshopper-like	43

43a.	Terminal appendages of abdomen forming a pair of pincers or forceps	44
43b.	Terminal appendages of abdomen not like this	45

44a.	Tarsi 3-segmented	Dermaptera
44b.	Tarsi 1-segmented	Diplura

45a.	Terminal appendages of abdomen long (much more than half the length of the abdomen)	46
45b.	Terminal appendages of abdomen short (less than half the length of the abdomen)	48

46a.	Abdomen with 3 terminal appendages (paired cerci and a median filament)	Thysanura
46b.	Abdomen with 2 terminal appendages (cerci)	47

47a.	Tarsi 3-segmented; terminal appendages of abdomen (cerci) unsegmented	Dermaptera
47b.	Tarsi 1-segmented; terminal appendages of abdomen (cerci) many-segmented	Diplura

48a.	Tarsi usually 5-segmented (though sometimes fewer on regenerated legs of Phasmida)	49
48b.	Tarsi with fewer than 5 segments on all legs	52

49a.	Front of head extended downwards to form a beak-like structure with jaws (mandibles) at its tip	Mecoptera
49b.	No such beak-like extension of the head	50

50a.	Prothorax much larger than the head	Dictyoptera
50b.	Prothorax and head of similar size (prothorax at most only slightly larger than the head)	51

51a.	Cerci 8-segmented and moderately long	Grylloblattodea
51b.	Cerci unsegmented and very short	Phasmida

52a.	Tarsi usually 4-segmented	Isoptera
52b.	Tarsi with fewer than 4 segments	53

53a.	Tarsi 1-segmented	Diplura
53b.	Tarsi 2- or 3-segmented	54

54a.	Tarsi 2-segmented	Zoraptera
54b.	Tarsi 3-segmented	55

55a.	Front tarsi with first segment greatly swollen; cerci 2-segmented	Embioptera
55b.	Front tarsi not swollen; cerci unsegmented	Phasmida

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Last revised January 2009