Key to adult insects
An adult female orange tip butterfly, Anthocharis cardamines. Only the adult males possess the orange tips to the wings that give this species its common name.
If you've found an insect and you don't know what it is then you can use the on-line Key below to find out what order your insect belongs to. It is a good idea to have the insect in a 'Bug Box' whilst you use the Key - it's much easier than relying on your memory. Please read all the text below before using the Key.
Limitations of the Key
- Important: This Key will only identify insects to a specific Order, it does not identify to species level (you'll require a specialised book for that or you'll need to use one of our identification services).
- The Key also refers to some groups (such as the Protura, Diplura and Collembola) which are considered to be non-insect hexapods rather than insects. These are still included in the key in order to make the key as useful as possible.
- The Key will only work for adult insects (the imago), it is not intended for juvenile insects, larvae or caterpillars so make sure you are trying to identify an adult insect.
- The Key may not be successful if used to identify insects outside the UK although in most cases it should still produce a correct identification.
- The Key uses some specialised terms to describe specific parts of an insect's body. An explanation of many of these terms can be found on the Insect body structure page or within the Insect fact files section.
The AES cannot be held responsible if the Key provides an incorrect identification, it is intended as a guide only - if you require a species level identification then please use our identification services or send the insect with comprehensive details of where you found it to the Entomology Department of your nearest University or Natural History Museum.
Non-members can use the Bug Club discussion forum however membership of this forum is not restricted and we cannot guarantee the help/advice offered.
Key to insect orders
Start at Question 1 and follow the links until you've identified your insect.
- Insect has wings? Go to 2
Insect wingless or with poorly developed (vestigial) wings. Go to 29
- One pair of wings. Go to 3
Two pairs of wings. Go to 7
- Body grasshopper-like, with enlarged hind legs and pronotum extending back over abdomen =
Orthoptera
Insects not like this. Go to 4
- Abdomen with 'tails'. Go to 5
Abdomen without 'tails'. Go to 6
- Insects <5mm long, with relatively long antennae: wing with only one forked vein = Hemiptera
Larger insects with short antennae and many wing veins: tails long = Ephemeroptera
- Fore wings forming club-shaped halteres = Strepsiptera
Hind wings forming halteres (may be hidden) = Diptera
- Fore wings hard or leathery. Go to 8
All wings membranous. Go to 13
- Fore wings tough apart from membranous tip = Hemiptera
Fore wings of uniform texture throughout. Go to 9
- Fore wings (elytra) hard and veinless, meeting in centre line. Go to 10
Fore wings with many veins, overlapping at least a little and often held roofwise over the body. Go to 11
- Abdomen ending in a pair of pincer-like cerci : elytra always short = Dermaptera
Abdomen without forceps: elytra commonly cover whole abdomen = Coleoptera
- Insects with piercing and sucking beaks = Hemiptera
Insects with chewing mouthparts: cerci ('tails') usually present. Go to 12
- Hind legs modified for jumping = Orthoptera
Hind legs not modified for jumping. Go to 49
- Tiny insects covered with white powder. Go to 14
Insects not like this. Go to 15
- Wings held flat at rest: mouth-parts adapted for piercing and sucking = Hemiptera
Wings held roofwise over body at rest: biting mouthparts = Neuroptera
- Small, slender insects with narrow, hair-fringed wings: often found in flowers = Thysanoptera
Insects not like this. Go to 16
- Head extending downwards into a beak = Mecoptera
No such beak. Go to 17 - Wings more or less covered with scales: coiled proboscis (tongue) usually present = Lepidoptera
Wings usually transparent although often hairy. Go to 18
- Wings with a network of veins, including many cross veins. Go to 19
Wings with relatively few cross veins. Go to 23
- Abdomen with long terminal threads. Go to 20
Terminal appendages short or absent. Go to 21
- Fore wings 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
- Antennae very short: body at least 25mm long = Odonata
Antennae longer: greater than width of head. Go to 22
- Tarsi 3-segmented = Plecoptera
Tarsi 5-segmented = Neuroptera
- Wings noticeably hairy. Go to 24
Wings not noticeably hairy. Go to 25
- All wings more or less alike: front tarsi swollen = Embioptera
Hind wings usually broader than fore wings: front tarsi not swollen = Trichoptera
- Tarsi with 4 or 5 segments. Go to 26
Tarsi with 1 - 3 segments. Go to 27
- All wings alike = Isoptera
Hind wings much smaller than fore wings = Hymenoptera
- Hind wings similar to or larger than fore wings: abdomen with cerci = Plecoptera
Hindwings smaller than fore wings: no cerci. Go to 28
- Tiny insects with at least 12 antennal segments = Psocoptera
Never more than 10 antennal segments: piercing and sucking beak present = Hemiptera
- Insects with slender, twig like body = Phasmatodea
Insects not like this. Go to 30
- Insects with grasshopper-like body and long back legs = Orthoptera
Insects not like this. Go to 31
- Small, soft-bodied insects living on plants, often under protective shield or scale = Hemiptera
Insects not like this. Go to 32
- Minute soil-living insects, <2mm long without antennae = Protura
Insects not like this. Go to 33
- Insects with cerci or other abdominal appendages. Go to 34
Insects with other appendages. Go to 41
- Abdominal appendages long and conspicuous. Go to 35
Abdominal appendages short or hidden under body. Go to 38
- Abdominal appendages forming pincers. Go to 36
Abdominal appendages not forming pincers. Go to 37
- Tarsi 3-segmented = Dermaptera
Tarsi 1-segmented = Diplura
- Abdomen with 3 long terminal appendages = Thysanura
Abdomen with only 2 terminal appendages = Diplura
- Tiny jumping insects, head points downwards forming a beak = Mecoptera
No sign of beak. Go to 39
- Small or minute insects with a forked springing organ (furcula) under rear of abdomen: generally found in soil or decaying vegetation = Collembola
Insects not like this. Go to 40
- Tarsi usually 4-segmented = Isoptera
Tarsi 3-segmented: front tarsi swollen = Embioptera
- 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
- Jumping insects flattened from side-to-side = Siphonaptera
Insects not flattened from side-to-side. Go to 43
- Insects of moderate size: head partly withdrawn into thorax. Go to 44
Small minute insects: head not withdrawn into thorax. Go to 45
- Antennae very short: very 'leggy' insects with strong claws well suited to clinging to a host mammal = Diptera
Antennae long: body somewhat circular, with less prominant legs and claws = Hemiptera
- Prothorax distinct: biting mouthparts = Mallophaga
Thoracic segments fused into one unit: sucking mouthparts = Anoplura
- Abdomen with pronounced 'waist': antennae often elbowed = Hymenoptera
No such features. Go to 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
- 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 (cornicles) near hind end: insects found on growing plants = Hemiptera - First pair of legs raptorial (used to grasp prey) and held close to the body at rest = Praying Mantids
Front legs not like this and body flattened = Cockroaches
References
This Key is based on the Keys that can be found in the following books.
Insects of Britain & Northern Europe
Michael Chinery
Collins Field Guide
ISBN 0-00-219918-1
The Practical Entomologist
Rick Imes
Aurum Press
ISBN 1-85410-209-5
Definitions to some of the terms used in this Key can be found in the Entomologists' Glossary