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When you want to identify an insect the first step is to find out in which Order it is classified. For this you can use a dichotomous key. A dichotomous key is a tool that uses paired statements or questions to guide you to the solution.
To use the key it will be necessary to have a good hand lens and you should be familiar with the terminology used for the different parts of an insect body. If you don't know a word or term, please have a look in the glossary.
Identification keys are a good starting point, but you should realize that there are hundred thousands of insect species in this world and among them there is a lot of variation. The keys cannot cover all this variation. When you have reached a solution, always double check the result by reading a detailed description of the insect Order.
| 1a | Insect with wings
(but the forewings could be partly or entirely stiffened as 'wing-covers' or 'wing-cases' and are not used for flying) |
2 | |
| 1b |
Insect without wings
(but there could be remnants of wings resembling small scales or pads) |
32 | |
| 2a | Insect with one pair of wings | 3 | |
| 2b | Insect with two pairs of wings | 9 | |
| 3a | The dorsal surface of the prothorax extends backwards over the abdomen; the hind-legs enlarged and modified for jumping; insect looks grasshopper-like in general appearance | Orthoptera | |
| 3b | Insect different | 4 | |
| 4a | The wings are horny or leathery (stiff or rigid) and are not used for flying | 5 | |
| 4b | The wings are membranous (flexible) and are used for flying | 6 | |
| 5a | The wings overlap at least a little in the centre-line and with obvious veins present | Phasmida | |
| 5b | The wings (elytra) meet in the centre-line (sometimes they are fused together) and without veins (note that the elytra may have longitudinal grooves or striae but these should not be confused with veins) | Coleoptera | |
| 6a | The abdomen has one or more long terminal appendages | 7 | |
| 6b | The abdomen is without terminal appendages | 8 | |
| 7a | The wings have only one forked vein; antennae are relatively long; small insect usually less than 5 mm long | Hemiptera | |
| 7b | The wings have many veins; antennae are short; larger insect | Ephemeroptera | |
| 8a | The thorax has a pair of club-shaped structures (halteres) situated just in front of the wings | Strepsiptera | |
| 8b | The thorax has a pair of club-shaped structures (halteres) lying just behind the wings (these halteres may be hidden by body hairs and other structures) | Diptera | |
| 9a | The forewings are partly or entirely horny or leathery and form stiffened covers for the membranous hindwings | 10 | |
| 9b | Both pairs of wings are membranous (flexible) and used for flying (sometimes the wings are feather-like rather than membranous or their membranous nature may be obscured by a covering of hairs, scales or waxy powder) | 16 | |
| 10a | The mouth-parts form a tube-like 'beak' (rostrum) which is used for piercing and sucking (this rostrum is usually folded backwards under the body when not in use) | Hemiptera | |
| 10b | The mouth-parts have jaws (mandibles) and are designed for biting and chewing | 11 | |
| 11a | The forewings overlap at least a little in the centre-line and usually with many veins present | 12 | |
| 11b | The forewings (elytra) meet in the centre-line and have no veins (note that the elytra may have longitudinal grooves or striae but these should not be confused with veins) | 14 | |
| 12a | The hind-legs are enlarged and modified for jumping; insect looks like a grasshopper in general appearance | Orthoptera | |
| 12b | The hind-legs are not modified for jumping and are usually similar in thickness to the middle-legs; insect is not grasshopper-like | 13 | |
| 13a | The prothorax is much larger than the head; cerci nearly always many-segmented and fairly prominent | Dictyoptera | |
| 13b | Prothorax and head are of similar size; cerci are not segmented and very short | Phasmida | |
| 14a | The forewings (elytra) are long and cover all or most of the abdomen | Coleoptera | |
| 14b | The forewings (elytra) are short and much of the abdomen remains exposed | 15 | |
| 15a | The abdomen has a pair of terminal pincers or forceps | Dermaptera | |
| 15b | The abdomen has no terminal pincers | Coleoptera | |
| 16a | The wings are very narrow without veins and fringed with long hairs (feather-like); tarsi are 1- or 2-segmented; small slender insect often found in flowers | Thysanoptera | |
| 16b | The wings broader with veins present; if wings are fringed with long hairs then tarsi are comprised of more than 2 segments (the wing veins of some insects may be much reduced and hardly visible or partly obscured by hairs, scales or waxy powder) | 17 | |
| 17a | The hindwings are clearly smaller than the forewings | 18 | |
| 17b | Both pairs of wings are similar in size or hindwings larger than forewings | 26 | |
| 18a | Wings and much of the body covered with white waxy powder; tiny insect usually less than 2-3 mm long | 19 | |
| 18b | Without powdery covering | 20 | |
| 19a | When at rest the wings are held flat over the body; the mouth-parts form a tube-like 'beak' (rostrum) for piercing and sucking (this rostrum is usually folded backwards under the body when not in use) | Hemiptera | |
| 19b | When at rest the wings are held roof-wise over the body; the mouth-parts have jaws (mandibles) and are designed for biting | Neuroptera | |
| 20a | The wings are more or less covered with very small scales; the mouth-parts when present are forming a coiled proboscis or 'tongue' | Lepidoptera | |
| 20b | The wings are usually transparent (wings without scales but often hairy); the mouth-parts are not forming a coiled proboscis | 21 | |
| 21a | The forewings have many cross-veins making a network pattern; the abdomen has 2 or 3 long thread-like terminal appendages | Ephemeroptera | |
| 21b | The forewings show relatively few cross-veins; the abdomen is usually without or with only very short terminal appendages (cerci) | 22 | |
| 22a | The wings are noticeably covered with hairs; insect looks moth-like in general appearance | Trichoptera | |
| 22b | The wings are not noticeably hairy (but wings may be fringed with hairs or tiny surface hairs may be seen if wings are inspected under a microscope or strong hand-lens) | 23 | |
| 23a | The mouth-parts form a tube-like 'beak' (rostrum) for piercing and sucking (usually the rostrum is folded backwards under the body when not in use; the abdomen sometimes has tubular outgrowths or cornicles near the hind end) | Hemiptera | |
| 23b | The mouth-parts has jaws (mandibles) and are designed for biting and chewing | 24 | |
| 24a | The tarsi are 4- or 5-segmented; hard-bodied insects with the abdomen often constricted at its base into a petiole or narrow 'waist' | Hymenoptera | |
| 24b | The tarsi are 2- or 3-segmented; small soft-bodied insect | 25 | |
| 25a | Antennae with at least 12 segments | Psocoptera | |
| 25b | Antennae with only 9 segments | Zoraptera | |
| 26a | The tarsi are 5-segmented | 27 | |
| 26b | The tarsi are 3- or 4-segmented | 29 | |
| 27a | The wings are noticeably covered with hairs; insect is moth-like in general appearance | Trichoptera | |
| 27b | The wings are not noticeably hairy (but tiny hairs may be seen if the wings are observed under a microscope or with a strong hand-lens) | 28 | |
| 28a | The front of the head is extended downwards to form a beak-like structure with jaws (mandibles) at its tip | Mecoptera | |
| 28b | Insect without such a beak-like extension of the head | Neuroptera | |
| 29a | The tarsi are 4-segmented | Isoptera | |
| 29b | The tarsi are 3-segmented | 30 | |
| 30a | The wings are noticeably hairy; the front tarsi are with the first segment greatly swollen | Embioptera | |
| 30b | The wings are not noticeably hairy; the front tarsi are simple | 31 | |
| 31a | The wings have many cross-veins, which makes a network pattern; wings are held away from the body at rest (either outstretched or folded vertically); the antennae are short and inconspicuous | Odonata | |
| 31b | The wings have relatively few cross-veins and are folded flat over the body when at rest; the antennae are long and slender (longer than the width of the head) | Plecoptera | |
| 32a | Small soft-bodied insect which lives on terrestrial plants with the body encased under a protective shield ('scale') or the body is partly covered with white waxy filaments or powder | Hemiptera | |
| 32b | Insect different | 33 | |
| 33a | Thoracic legs are absent or enclosed in a membrane preventing any movement | (Larvae and pupae of most Orders of Endopterygota) | |
| 33b | Thoracic legs are present and fully functional | 34 | |
| 34a | The abdomen has false-legs or prolegs (prolegs are fleshy leg-like structures that are different from and additional to the jointed legs of the thorax); the insect looks like a caterpillar in general appearance | 35 | |
| 34b | The abdomen has no prolegs; the insect is not caterpillar-like in appearance | 37 | |
| 35a | Abdomen with not more than 5 pairs of prolegs | Larvae of Lepidoptera | |
| 35b | Abdomen has at least 6 pairs of prolegs | 36 | |
| 36a | The head has a single small eye (ocellus) on each side | Larvae of Hymenoptera | |
| 36b | The head has several small eyes (ocelli) on each side | Larvae of Mecoptera | |
| 37a | The insect lives in a terrestrial habitat or on the surface of water (not underwater) | 38 | |
| 37b | The insect is truly aquatic (living underwater) | 70 | |
| 38a | The abdomen has cerci or other terminal appendages (but be careful not to confuse terminal hairs or bristles with cerci) | 39 | |
| 38b | The abdomen does not have such terminal appendages (but it may have small appendages on proximal segments or a pair of tubular outgrowths or cornicles near the hind end) | 56 | |
| 39a | The abdomen has 6 or fewer segments; usually the abdomen has a forked terminal appendage (springing organ) folded under the rear end when not in use | Collembola | |
| 39b | The abdomen has more than 6 segments (usually 8 or more are clearly visible); the terminal appendages are of a different form | 40 | |
| 40a | The antennae are short and often inconspicuous (the same length as the head or shorter) | 41 | |
| 40b | The antennae are long and conspicuous (usually they are much longer than the head) | 42 | |
| 41a | The tarsi have at least 3 segments (usually they are 5-segmented) | Phasmida | |
| 41b | The tarsi have fewer than 3 segments (often they are reduced to single or paired claws on the end of each leg) | Larvae of Coleoptera | |
| 42a | The hind-legs are enlarged and modified for jumping; insect looks like a grasshopper in general appearance | Orthoptera | |
| 42b | The hind-legs are not modified for jumping; usually the hind-legs are similar in thickness to the middle-legs; insect does not look grasshopper-like | 43 | |
| 43a | The terminal appendages of the abdomen form a pair of pincers or forceps | 44 | |
| 43b | The terminal appendages of the abdomen are different | 45 | |
| 44a | The tarsi are 3-segmented | Dermaptera | |
| 44b | The tarsi are 1-segmented | Diplura | |
| 45a | The terminal appendages of the abdomen are long (much more than half the length of the abdomen) | 46 | |
| 45b | The terminal appendages of the abdomen are short (less than half the length of the abdomen) | 48 | |
| 46a | The abdomen has 3 terminal appendages (these are a paired cerci and a median filament) | Thysanura | |
| 46b | The abdomen has only 2 terminal appendages (cerci) | 47 | |
| 47a | The tarsi are 3-segmented; the terminal appendages of the abdomen (cerci) are unsegmented | Dermaptera | |
| 47b | The tarsi are 1-segmented; the terminal appendages of the abdomen (cerci) are many-segmented | Diplura | |
| 48a | The tarsi are usually 5-segmented (but sometimes fewer on regenerated legs of Phasmida) | 49 | |
| 48b | The tarsi have fewer than 5 segments on all legs | 52 | |
| 49a | The front of the head is extended downwards to form a beak-like structure with jaws (mandibles) at its tip | Mecoptera | |
| 49b | Insect without such a beak-like extension of the head | 50 | |
| 50a | The prothorax is much larger than the head | Dictyoptera | |
| 50b | The prothorax and head are of similar size (the prothorax is at most only a little bit larger than the head) | 51 | |
| 51a | The cerci are 8-segmented and are moderately long | Grylloblattodea | |
| 51b | The cerci are unsegmented and are very short | Phasmida | |
| 52a | The tarsi are usually 4-segmented | Isoptera | |
| 52b | The tarsi have fewer than 4 segments | 53 | |
| 53a | The tarsi are 1-segmented | Diplura | |
| 53b | The tarsi are 2- or 3-segmented | 54 | |
| 54a | The tarsi are 2-segmented | Zoraptera | |
| 54b | The tarsi are 3-segmented | 55 | |
| 55a | The front tarsi have a first segment which is greatly swollen; the cerci are 2-segmented | Embioptera | |
| 55b | The front tarsi are not swollen; the cerci are unsegmented | Phasmida | |
| 56a | The insect lives as a parasite on a warm-blooded animal or it is closely associated with such an animal (for example it lives on the body or in the nest or den of a bird or mammal) | 57 | |
| 56b | The insect is not parasitic on a warm-blooded animal | 61 | |
| 57a | The insect body is flattened from side to side; jumping insect | Siphonaptera | |
| 57b | The insect body is flattened from top to bottom | 58 | |
| 58a | The head is partly withdrawn into the thorax | 59 | |
| 58b | The head is not withdrawn into the thorax | 60 | |
| 59a | The antennae are short and inconspicuous (they are much shorter than the head); legs with strong and distinctly hooked tarsal claws | Diptera | |
| 59b | The antennae are long and conspicuous (they are more than twice the length of the head); legs have small and only slightly curved tarsal claws | Hemiptera | |
| 60a | At least the prothorax is distinct from the other thoracic segments; the legs have small tarsal claws; the mouth-parts have jaws (mandibles) and are designed for biting | Mallophaga | |
| 60b | All the thoracic segments are fused into a single unit; the legs have large tarsal claws which can close tightly against the legs; the mouth-parts form a tube-like proboscis for piercing and sucking (this proboscis is retracted within the head when not in use) | Siphunculata | |
| 61a | Insect without antennae (very small soil-living insects usually less than 2 mm long) | Protura | |
| 61b | Antennae are present | 62 | |
| 62a | The abdomen is strongly constricted at its base into a narrow petiole or 'waist'; the antennae are often bent into an elbowed shape | Hymenoptera | |
| 62b | The abdomen is not constricted into a 'waist'; the antennae are more or less straight | 63 | |
| 63a | The body is covered with dense scales and flattened hairs | Lepidoptera | |
| 63b | The body is bare or with sparse bristle-like hairs | 64 | |
| 64a | The mouth-parts form a tube-like proboscis or rostrum for piercing and/or sucking (this proboscis is usually folded backwards under the head when not in use) | 65 | |
| 64b | The mouth-parts are with jaws (mandibles) and designed for biting and/or chewing | 67 | |
| 65a | The tarsi are usually 5-segmented | Diptera | |
| 65b | The tarsi have fewer than 5 segments | 66 | |
| 66a | The proboscis is small and cone shaped (it is much shorter in length than the head) (small slender insect often found in flowers) | Thysanoptera | |
| 66b | The proboscis or rostrum is long and jointed (it is nearly always longer than the head) (abdomen sometimes with tubular outgrowths or cornicles near the hind end) | Hemiptera | |
| 67a | The antennae are short and often inconspicuous (length of the antennae is at most about the same length as the head) | 68 | |
| 67b | The antennae are long and conspicuous (they are much longer than the head) | 69 | |
| 68a | The abdomen has 6 or fewer segments | Collembola | |
| 68b | The abdomen has more than 6 segments (usually 8 or more segments are clearly visible) | (Larvae of various Orders) | |
| 69a | The head is narrower than the body; the mandibles are very long and protruding forward well in front of the head (the mandibles are clearly visible from above) | Larvae of Neuroptera | |
| 69b | The head is as wide or nearly as wide as the body; the mandibles are small and not protruding in front of the head (they are not visible from above) | Psocoptera | |
| 70a | The mouth-parts with a tube-like 'beak' or with long stylets and are designed for piercing and sucking | 71 | |
| 70b | The mouth-parts have jaws (mandibles) and are designed for biting and/or chewing | 72 | |
| 71a | The mouth-parts form a robust tube-like 'beak' (rostrum) folded backwards under the body when not in use | Hemiptera | |
| 71b | The mouth-parts form a pair of long and slender stylets extending more or less straight forward in front of the head between the antennae and about as long or longer than the antennae | Larvae of Neuroptera | |
| 72a | Head has a hinged grasping organ (or 'mask') that can stick out; this organ bears large terminal claws (normally it is folded beneath the head when not in use) | Nymphs of Odonata | |
| 72b | No hinged grasping organ or 'mask' beneath the head | 73 | |
| 73a | The abdomen has pairs of feather-like or flat plate-like lateral appendages on some segments (gill filaments) and 3 long terminal appendages (paired cerci and a median filament) | Nymphs of Ephemeroptera | |
| 73b | Insects without this combination of features | 74 | |
| 74a | The abdomen is without lateral appendages but with 2 long terminal appendages (cerci); the antennae are long and slender (they are much longer than the head) | Nymphs of Plecoptera | |
| 74b | Insects without this combination of features | 75 | |
| 75a | The abdomen has pairs of multi-jointed feather-like lateral appendages on some segments (gill filaments) and sometimes a single terminal appendage | Larvae of Neuroptera | |
| 75b | The abdomen is without lateral appendages (gill filaments) or if such appendages are present then they are always unjointed | 76 | |
| 76a | The last abdominal segment has a pair of fleshy appendages each bearing a strong claw; the middle- and hind-legs are longer than the width of the thorax; the body is often enclosed in a tubular case made from small pebbles or other debris | Larvae of Trichoptera | |
| 76b | Insects without this combination of features | Larvae of Coleoptera | |
