It’s a bee . . . It’s a wasp . . . No, it’s Hover Fly!
Hover flies get their name from their unique ability to hover, suspended in midair, then dart a short distance very quickly, only to hover again. They’re the helicopter version of flying insects. And they can fly backwards, an ability few insects possess.
Hover flies true flies within the Order Diptera. Allograpta obliqua is the most commonly seen hover fly in our area. Hover flies are also known as syrphid flies and flower flies and are quite plentiful in North America. While hover flies are very widespread in our area, their role as an important beneficial is underappreciated.
Adult hover flies are important pollinators and can be found feeding at flower blossoms or around aphid colonies, where they lay their eggs. The larvae of hover flies are important predators of pests, such as aphids, scales, thrips and caterpillars.
They are rivaled only by ladybird beetles and lacewings. When hover fly larvae populations are high, they may control 70 to 100% of an aphid population. Aphids alone cause tens of millions of dollars of damage annually to crops worldwide, so the aphid-feeding hover flies are being recognized as potential agents for use in biological control.
Many species of hover flies mimic bees or wasps in appearance. Some even go so far as to wave their front legs in front of their face to imitate the antennae of the potter wasps. However, one can easily separate the hover flies from bees or wasps by their wings: flies have two wings and wasps and bees have four.
Hover flies can also be distinguished by looking at the head—if it looks like a fly's head, then more than likely it is a fly. It is thought that this guise protects hover flies from falling prey to birds and other insectivores that avoid eating true wasps because of their sting.
Like all flies, hover flies have a complete metamorphosis—egg, larval, pupal and adult stages. Adults occur throughout the year in the Texas Upper Gulf Coast, but they become much more abundant during spring and summer. They often are abundant even during the winter season when moderate temperatures prevail.
The life cycle of hover flies varies from as little as three weeks in summer to nine weeks in winter. The egg is a creamy white, elongated oval, hatching in two to three days during the summer and within eight days in the winter, in the southern US.
Hover fly larvae are legless and wormlike, colored a dull green, with two narrow whitish long stripes about one-half inch long. Larvae are smooth-skinned and sausage-shaped. The head area is pointy and the tail looks like it's been cut off flat. Larvae should be protected from insecticidal sprays. Even the use of insecticidal soaps should be avoided as it is harmful.
The larvae crawl about exposed on vegetation feeding on aphids. The prey is grasped by the larvae’s jaws, raised into the air and its body contents drained.
The larva fastens itself to a leaf or twig when it is ready to pupate. The color of the pupa changes from green to the color of the adult hover fly. Most pupa overwinter in soil or under fallen leaves. Hover fly larvae are not as well-known for their role as beneficials as lady beetle larvae are as their pupal stage is overlooked. There are very few photos to be found of the pupal stage compared to other common beneficial insects. We are fortunate that one of our photographers has become adept at finding and photographing the pupal stage of the hover fly.
The adults are small- to medium-sized flies, with an average body length of up to 5/8". They are brightly colored with yellow and black bands of equal width around the body and one pair of clear wings. Hover flies have large, compound eyes, which nearly cover their big head and small antennae. Winged adults are active during warm months, when they use flowers as mating sites and energy sources.
Most species of hover flies are beneficial because the larval stages are predaceous on insect pests such as aphids, scale insects, mealybugs and thrips. In addition, the adult stage pollinates flowers. That’s a win-win situation for gardeners.
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
All digital photographs are the property of the Galveston County Master Gardener Association, Inc. (GCMGA) 2002-2015 GCMGA - All Rights Reserved.