Lately we have been seeing a lot of flying, annoying bugs that look like tiny yellow jackets or bees. They pester you relentlessly, landing on your skin and being seen in large swarms in our backyards, especially near our gardens. They can be so plentiful that people run from them out of fear.
Most likely the culprit we see is a hoverfly, a harmless insect which is mistaken by its banded black-and-yellow coloring (a highly effective defense mechanism against predators like birds) for a wasp. Unlike wasps they have only two wings and no waist.
The hoverfly is completely benign and a very important pollinator. Their larvae eat aphids which are destructive to many plants. Its mouth parts are designed for mopping-up; so they can’t bite. They don’t sting, don’t make nests and won’t make you itch.
They can cause the disease Myiasis in sheep and very rarely in humans. It’s caused by the maggots feeding off of feces or open wound areas, generally only where there are poor sanitary practices such as in Africa and South America. It’s a common practice to remove a sheep’s tail early in their life, to help prevent this disease as well as others.
There are around 6,000 species of hoverflies, ranging in size from 5-20 mm long and are sometimes called flower flies in the U.S., or syrphid flies, and make up the insect family Syrphidae. When they fly their wings and short, stubby antennae are very difficult to observe but their behavior will be very different from a bee. These flies hover and move erratically; bees generally move slowly from flower to flower, and do not hover in one place.
Hoverflies are active during the day, mostly in the summer months. Adults feed mainly on nectar and pollen. Hoverflies are one of the few kinds of insects that can digest pollen, which is a protein rich source for the eggs. They particularly like flat-headed flowers, such as daisies, yarrow and members of the carrot family.
They overwinter as pupae in the soil or above ground in leaves and plant material. Adults emerge in May and June and lay eggs on leaves and stems of plants infested with prey. Larvae feed for 7 to 10 days, and then drop to the soil to pupate. A life cycle is completed in 16 to 28 days and there are 3 to 7 overlapping generations each year. The larvae feed on soft-bodied insects, particularly aphids. As many as 400 aphids may be consumed by one larva during its development.
Next time you see a hoverfly, don’t panic or be scared. Having them near your garden is a good thing.