Ann Sherlock dropped by last week with a couple of insect samples and wanted to know what they were. One of her samples was taken from a huge swarm of insects that decided to reside on her maple tree. Lucky for Sherlock, the swarming bugs are not a pest of maple or any other plant for that matter. However, they are often a nuisance to homeowners living near ponds and lakes, which is applicable to many Warren County residents. The swarming insects were Chironomid midges.

Perhaps anyone living near a lake has experienced these bugs before, as they are quite common.

Chironomid midges are small mosquito-like flies, which vary in length from 2 to 18 millimeters depending on the species. They range from shades of light, pale green to almost black. Swarms of midges can be seen hovering, particularly in the early morning or evening, near lake shorelines and almost anywhere else near water. Unlike mosquitoes, chironomid midges do not bite, nor do they carry disease.

Unlike mosquito larvae, which live mostly at the water surface and depend on quiet water in order to breathe, chironomid midge larvae live at the bottom or on submersed plants and objects. Their food consists of plankton algae and decaying matter. Midge larvae may number several thousand per square meter and adult midges may survive up to a week. Adults do not feed, and emerge only to mate, lay eggs and die.

Chironomid midges have four life stages: egg, larva, pupa and adult. The life cycle ranges from less than a week to more than a year. Adults begin emerging in late spring and finish in early fall. Chironomid midges mate mostly in aerial swarms. They lay eggs shortly thereafter in gelatinous packets which expand into complicated structures after placement in water. Egg masses either sink to the bottom or become attached by a gelatinous anchor cord to submerged plants and structures. Each egg mass contains from 100 to 2,000 eggs. Eggs usually hatch within 24 to 36 hours.

Chironomid midge larvae play a beneficial role in the aquatic food web breaking down organic sediments. Birds prey on adult midges, and both larvae and adults are important as fish food.

Chironomid midges, although basically harmless, become a severe nuisance when their numbers become excessive. The most common nuisance comprises dense midge swarms that are attracted to light and rest in shrubbery, on patio surfaces, and on the sides of homes. This nuisance is often enhanced by the accumulation of large numbers of spiders.

Management of chironomid midges is probably impractical. Where midges create a frequent nuisance, some relief may be achieved by strategic lighting or shrubbery placement. By situating bright security lights between the midge source and the site of concern, and using yellow incandescent bulbs at the site, most midges will be intercepted. Likewise, a windbreak barrier of trees and shrubs may serve as an effective alternate midge resting site between the source and the area of concern — usually one’s home.

John C. Coccaro is county Extension director. Write to him at 1100-C Grove St., Vicksburg, MS 39180 or call 601-636-5442. E-mail him at jcoccaro@ext.msstate.edu