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How many types of insects are there in the world? – Sawyer, age 8, Fuquay-Varina, North Carolina
Exploring anywhere on Earth, look closely and you’ll find insects. Check your backyard and you may see ants, beetles, crickets, wasps, mosquitoes and more. There are more kinds of insects than there are mammals, birds and plants combined. This fact has fascinated scientists for centuries.
One of the things biologists like me do is classify all living things into categories. Insects belong to a phylum called Arthropoda – animals with hard exoskeletons and jointed feet.
All insects are arthropods, but not all arthropods are insects. For instance, spiders, lobsters and millipedes are arthropods, but they’re not insects.
Instead, insects are a subgroup within Arthropoda, a class called “Insecta,” that is characterized by six legs, two antennae and three body segments – head, abdomen and the thorax, which is the part of the body between the head and abdomen.
The mandibles of the ants are its jaws; the petiole is the ant’s waist.
Vector Mine/iStock via Getty Images Plus
Most insects also have wings, although a few, like fleas, don’t. All have compound eyes, which means insects see very differently from the way people see. Instead of one lens per eye, they have many: a fly has 5,000 lenses; a dragonfly has 30,000. These types of eyes, though not great for clarity, are excellent at detecting movement.
What is a species?
All insects descend from a common ancestor that lived about about 480 million years ago. For context, that’s about 100 million years before any of our vertebrate ancestors – animals with a backbone – ever walked on land.
A species is the most basic unit that biologists use to classify living things. When people use words like “ant” or “fly” or “butterfly” they are referring not to species, but to categories that may contain hundreds, thousands or tens of thousands of species. For example, about 18,000 species of butterfly exist – think monarch, zebra swallowtail or cabbage white.
Basically, species are a group that can interbreed with each other, but not with other groups. One obvious example: bees can’t interbreed with ants.
But brown-belted bumblebees and red-belted bumblebees can’t interbreed either, so they are different species of bumblebee.
Each species has a unique scientific name – like Bombus griseocollis for the brown-belted bumblebee – so scientists can be sure which species they’re talking about.
This is what a dragonfly looks like up close.
Dieter Meyrl/E+ via Getty Images
Quadrillions of ants
Counting the exact number of insect species is probably impossible. Every year, some…
