Flies with mohawks are out to save your garden!
A tachinid fly looks like a small, sturdy house fly with a mohawk on its rear end. Others are unassuming tan-colored triangular flies. While yet others are somewhere between those extremes. These tiny beneficial flies use many common garden pests to feed their young. Let’s find out how.
Like other true flies (Diptera), tachinids (Tachinidae) have two wings. They are usually a bit smaller than houseflies, with spiky hairs on their rear ends that point backwards. There are thousands of species of tachinid fly. They may be black, tan, brown, grey, or striped. Eggs can be dark, or pale, or white, and oblong. The larva, or maggot, is a stubby, naked white, yellow, or orangish wormlike creature. The pupae are hidden in hard, reddish-brown, oblong casings, often found in the soil.
Tachinids as parasitoids
Tachinid flies are second only to parasitic wasps in pest control. Different tachinid species make use of different hosts in a number of ways. Most are parasitoids, which means they end up killing their host, while some are parasitic, which means the host may live. Tachinid flies parasitoid host insects to provide a guaranteed food source for their offspring. To parasitoid a garden pest, tachinid flies use several different methods. They may lay eggs on leaves favored by preferred caterpillars. When the larvae hatch, they are consumed by the caterpillar along with the leaf. Once inside the host, the larvae (maggots) begin their own feeding. Other tachinid species glue their eggs to the body of a host. When the eggs hatch, the maggots start feeding. Yet others using a piercing ovipositor (egg depositor organ) to inject the host with the eggs. Maggots feed until they are ready to pupate. Then, they drop to the ground and a hard casing forms to protect them as they morph into an adult fly.
You can attract tachinid flies to your garden or landscape by providing pollen and nectar for the adults with insectary plants, such as flat-topped (carrot, dill, yarrow) and composite (rudbeckia and aster) flowers. These beneficial insects also feed on aphid honeydew.
So, before you grab the fly swatter, take a closer look to see if that picnic pest is sporting a mohawk on its rear end.
You can grow a surprising amount of food in your own yard. Ask me how!