Tom Turpin
Professor of
Purdue University







In Defense of the Fly

It has often been said that the fly is the most hated of all insects. So what insect is the fly? There are a lot of insects called "flies" in this world. We have butterflies, dragonflies, dobsonflies, sawflies, caddisflies and stoneflies. But, in spite of their name and the fact that they do fly, these insects aren't really flies.

Historically, the word "fly," based on the Old English word "fleoge," was used for any flying insect. Scientifically, the word fly has come to be used today strictly for insects classified in the order Diptera. These insects have only two wings, hence the inclusion of "di" for two in their order name. So, any insect that is not a dipteran is not really a fly. They may be able to fly, but they are not flies!

To make it even more confusing, not even all Diptera are called flies. For instance, mosquitoes and midges are two-winged insects and are classified as Diptera but are not generally called flies.

The mouthparts of Diptera are characterized as a sucking type. That compares to the chewing mouths found in grasshoppers or the siphoning mouths possessed by butterflies. Some fly species, like the common house fly, sponge liquids before sucking them up. But other flies have the ability to pierce before sucking. That means some Diptera can bite. Appropriately, such flies are known as biting flies.

It seems likely that biting behavior on the part of flies might even have been the basis for the Latin word for fly -- "musca." This Latin root is found in the name of a gun called a musket. Aristotle recognized that flies bite when he stated that flies have the bite in the head, compared to bees that have the bite in the rear. The common house fly has the Genus name of musca , even though it is one of the flies that cannot bite.

Biting behavior of some flies and the presence of fly maggots in dead animals and decaying material have certainly contributed to the reputation of flies as a dreaded insect. There are negative references to flies in the Bible, including the well-known plague of flies endured by the ancient Egyptians. Many historical writers, including Shakespeare, made reference to worms -- most likely fly maggots -- consuming flesh. Beelzebub, the devil, is called the "lord of the flies." Indeed, the fly has had a long and ignominious history.

It is not surprising that humorist Mark Twain joined the throng of fly-bashers when he wrote: "Not one of us could have planned the fly, not one of us could have constructed him, and no one would have considered it wise to try, except under an assumed name."

In similar disdain, Ogden Nash pens: "God in his wisdom made the fly/ And then forgot to tell us why."

Maybe the disgust is justified. After all, the tse tse fly is the vector of African sleeping sickness. Mosquitoes are scientifically flies, and these two-winged biters transmit malaria and yellow fever, among other diseases, and have contributed to millions of human deaths over the years. One of the most damaging crop pests of the 19th century was the Hessian fly. Thomas Say gave the scientific name Mayetiola destructor to this insect because of devastation it inflicted on the wheat crop of North America.

Flies have earned their reputation as some of nature's most despicable creatures! But like almost everything else in this world, there's always the other side of the coin. As a group, there are many species of flies that are not troublemakers. In fact, some flies are beneficial.

Immature flies frequently feed in dead and decaying organic material and play an important role in recycling nutrients. Maggots are the primary reasons that animal carcasses disappear quickly during warm summer months. Almost all adult flies and their larvae can, and frequently do, become food items for other animals, such as birds, frogs, toads and fish. Even a few plants, including the aptly-named venus fly trap, consume insect meals. Larvae of syrphid flies are biocontrol agents. These insects are predators on aphids, which are plant pests.

So, in defense of flies, it can always be said that these insects are important to the balance of nature. And, they help keep dead animal carcasses from accumulating on the side of the road. That has got to be a good thing!


Writer: Tom Turpin
Editor: Olivia Maddox