During my visit with the 2nd grade entomologists at Central Valley Elementary School I had the chance to explain how scientist identify the more common orders of insects. I used an insect identification sheet developed by Anita Sanchez to organize our discussion. Unfortunately there was not enough time to cover all seven of the orders of insects that were shown. Here is a review of these common orders of insects, the names entomologists use for them and how these names help us identify them.
Butterflies and Moths – are called Lepidoptera, which means scale wing. If you’ve ever held a moth or butterfly you might have noticed the dusty powder that was left on your fingers. This powder is actually scales from the wings and body of the insect. These scales give color and strength to the wings. Butterflies and moths go through complete metamorphosis, which means they start off as an egg that hatches into a larva. The larva of moths and butterflies are often called caterpillars. The larvae eat and grow. When they are too big for their exoskeleton skin they shed, or molt the skin. Their new skin has room for them to grow. A larva can molt several times before it molts into a pupa. The pupa of a butterfly is called a chrysalis. The pupa of a moth is called a cocoon. Inside the pupa the larva is undergoing a complete change of its body growing all the things it will have as an adult, especially wings. When it emerges from the pupa it will pump up its wings so that they spread and flatten out. When the wings are dry the adult insect flies away to mate and lay eggs.
Bugs – are called Hemiptera, which means half wing. They get this name because the two wings they have are half thick, near the body and half thin further from their body. All bugs are insects but not all insects are bugs. To tell if it is a bug look for a triangle shape on the back of the insect where their thorax meets their abdomen. Bugs undergo what is called incomplete metamorphosis. When a bug hatches from the egg it doesn’t look worm-like, like a caterpillar or maggot. The newly hatched bug looks quite a bit like an insect with three body parts, antenna and six legs. The one thing it will not have is wings. This young bug is called a nymph. The nymph eats and grows. When it is too big for its exoskeleton it molts the skin and emerges a little larger. Upon its last molt it will emerge from the old exoskeleton but now have wings that will spread out, flatten and dry. Once dry the adult bug flies off to look for mates and lay eggs.
Ants, Bees, Wasps and Hornets – are called Hymenoptera, which mean thin skin wing. The hymenoptera have four thin skin, or membranous wings. Many of them, for example ants and honeybees, live in large groups or colonies. In these colonies there is one female that lays the eggs. This is the queen. She will have many daughters, often called workers, that will never lay eggs. In the case of ants these daughters will never have wings. They take care of the queen, feed the larvae and build and protect the nest. At certain times of the year the queen will lay eggs that will grow into adult queens and drones (the males). These adults will have wings. They live in the nest only a few days then fly away to find mates. After they mate the drones will soon die. The queens will start a new nest. The first larvae to hatch will be fed extra eggs that the queen lays for food. After undergoing complete metamorphosis, these first larvae will emerge as worker ants, daughters of the queen, that will now take over building and caring for the nest and all the ants living in it. The queen will spend the rest of her life laying eggs. Some queen ants can live up to 10 years and lay a million eggs in their lifetime.
Flies – are called Diptera, which means two wings. All flies have two wings. Some flies look like bees, yellow bodies with black stripes. Some bees look like flies. The way to tell them apart is to count their wings. Bees have four wings. Flies have two wings. Many insect have fly in their name but are not really flies. Generally speaking if the name is compound, butterfly, dragonfly, mayfly, the insect is not a true fly or dipteran. True flies will have names that are not compound such as house fly, deer fly or black fly. The flies go through complete metamorphosis. The larvae of flies are called maggots.
Dragonfly – are called Odonata, which means toothed. The dragonflies get this name for their predatory behavior, eating many small insects and other animals, both when they are nymphs in the water and adults flying around in the air. One of their favorite foods is mosquitoes. I have watched dragonflies at my pond chase and catch deer flies in mid-air. Dragonflies are not true flies. They undergo incomplete metamorphosis.
Beetles – are called Coleoptera, which means shield wing. The beetles have four wings, two for flying and two that serve as shields that protect the flying wings. When a beetle takes off it lifts open it’s shield wings, unfolds it’s flying wings and flies off. When the beetle lands it folds up it’s flying wings and then closes down it’s shield wings. When the shield wings are closed they meet in a long line down the back of the beetle’s abdomen. The best beetle to see this happen is the lady bug (notice that the lady bug is actually a beetle called the lady bird beetle – it does not have a triangle shape on it’s back like the true bugs, the hemiptera). Beetles go through complete metamorphosis. Beetle larvae are called grubs.
Grasshoppers and Crickets – are called Orthopter, which means straight wing. They get this name because adult grasshoppers have wings that are folded like a hand fan and thus appearing to be straight. Grasshoppers undergo incomplete metamorphosis, hatching out of the eggs as nymphs that look like little tiny grasshoppers. We caught one of these nymphs in our entomology expedition outside.
These seven are among the more common orders of insects. There are about 28 orders of insects. I say about because scientist do not all agree on some of the orders of insects. Some scientist want to combine some orders, while other scientists think it is best to keep them separate. Some of the other orders of more familiar insects include mayflies (Ephemeroptera), fleas (Siphonaptera), cicadas (Homoptera) and earwigs (Dermaptera).
Spiders are not insects. They have eight legs and two body parts (a cephalothorax – which means head-thorax and an abdomen). Entomologists study spiders for several reasons. One reason is that they are relatives of insects. Spiders and insects are arthropods. Other arthropods include centipedes, millipedes and crustaceans (crabs, lobsters, crayfish and shrimp). All arthropods have exoskeletons that are shed or molted when the animals outgrow them. Another reason entomologists study spiders is that where ever you capture insects you will also capture spiders. That is because spiders prey upon insects (although there are some insects that turn the dinner table around and eat spiders).
Insects are the most numerous of all animals. They live all around us, even in our houses. That means there are many insects that can be studied without have to travel far. You can study ants on the playground, beetles in an old rotting log, or caterpillars on leafy branches. When you do these studies you are being an entomologist.
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