Identifying Insects
What are the most important insect features?
Insects are the most populous animal on plant earth! Insects live across the globe including in the Arctic. Insects are also wonderfully diverse! Some variation includes long bodied stick insects, beetles with large mandibles, butterflies with colorful wings, and cute fuzzy bees! So, how do you know if something is an insect or whether it's another type of invertebrate?
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Below are a variety of characteristics you can use to determine if an invertebrate is an insect or something else. Always use the three and up rule when identifying anything. in this case, if the invertebrate you are looking at has at least three three of these characteristics, then you can be fairly certain it is an insect and not an arachnid, worm, millipede, or centipede! The features listed below are important features for identifying all insects, so become familiar with these features and the terminology before moving onto the next identification guide.​
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The Tagmata
The photo to the left shows a carpenter bee with three distinct tagmata. The first tagmata is the head, which has large compound eyes and antennae. In this photo, the head is the farthest to the right and is black and shiny in colour. The second tagmata is the thorax which is covered in yellow hair on this bee (except for a small bald spot on it's back). the final tagmata is the abdomen which is shiny black with several 'sections' in this picture. All insects have three tagmata. If the invertebrate you are examining has less than three tagmata, it is likely a spider. If it has many more tagmata, it could be a centipede or a millipede.
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"Melissodes sp." by cricketsblog is licensed under CC BY 2.0
Antenna
The photo shows a male Melissodes bee. These bees have very long antennae compared to the females. The antennae of insects acts as an olfactory organ, so it detects odour molecules in the air. Many insects have humidity sensors in their antennae to detect moisture in the air. Finally, mosquitoes can use their antennae to detect sounds with their antennae and flies can use their antennae to gauge air speed while flying. If the invertebrate you are looking at has no antennae, you may be face to face with a spider or worm.
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Insect Eyes
The photo shows a big eyed fly. The head is in the left in this picture and is almost completely covered by the large eyes. These eyes give the fly a large range of vision to stay away from a swatting hand. Many insects have compound eyes. These eyes are comprised of many facets (also known as ommatidia). While insects cannot form a focused image of the environment around them, their eyes are fantastic at sensing movement. Compound eyes are a fantsastic indicator that the invertebrate you are looking at is indeed an insect.
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"Bruce Archibald" by SFU - Communications & Marketing is licensed under CC BY 2.0
"praying mantis" by shivanayak is marked with CC BY-SA 2.0.
Insect Legs
The photo shows a praying mantis with all six of its legs. These legs are all attached to the praying mantis' thorax (the middle tagmata). Adult insects all have 6 legs. Insects have adpted them for a variety of functions. One of the best examples of this is bumble bees, which have antennae cleaners on their fore legs, and pollen baskets (also known as corbicula) on their hind legs. If the invertebrate you are looking at has more than 6 legs, it is not an insect. Invertebrates with more than 6 legs include spiders, centipedes, millipedes, and ticks.
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Wings
Many adult insects have wings. Wings vary in size, shape, and color. Butterflies have small scales on their wings which give them their color. Flies only have one pair of wings. Bees have two pairs of wings that are membranous. The picture shows a carpenter bee with beautiful purple and blue wings. Wings make it easy to determine if an invertebrate is an insect as all invertebrates with wings are insects. Some insects do not have wings, but these are generally the exceptions to the rule.
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"Xylocopa valga ? Female. Xylocopidae" by gailhampshire is marked with CC BY 2.0.
Page information
Author: Melissa Platsko
Date published: April 2, 2022
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