Related Topic: Honey Bee Parasites, Pests and Predators - New slide set, viewable on Web

Braula coeca, or bee louse, is an external parasite of adult bees. The adult lice are small (slightly smaller than the head of a straight pin), reddish brown, wingless flies. They first appeared in the United States as "hitchhikers" on the bodies of imported queens. While several adult flies may live on a queen, usually only one lives on a worker. Bee lice seem to prefer nurse bees; only rarely do they live on drones. Braula move rapidly over the body surface, settling on the dorsal surface at the junction of the bee's thorax and abdomen. They remain there until a hunger response causes them to crawl up to the bee's head near its mouthparts. This movement seems to irritate the bee, causing it to regurgitate a drop of nectar. Braula then inserts its mouthparts into those of its benefactor and takes its food. Bees actively try to remove the lice.

The louse lays its eggs on the cappings of honey storage cells during May through July. After oviposition, the adults die. Upon hatching, the young larvae burrow into the cappings. As the larvae grow, their tunnels lengthen and broaden; at this stage the infestation is easiest to observe. The larva pupates inside the tunnel after making a line of weakness in the wax to aid in its emergence as an adult. Soon after emergence, about twenty-one days later, the young adult crawls upon a bee. The diet of the larva appears to be wax and perhaps pollen grains incorporated into the wax by worker bees. In Pennsylvania bee lice overwinter as adults and do not appear on queens until June.

Braula's damage to a colony of honey bees is limited. The amount of food taken by the larvae and adults is negligible. However, the appearance of comb honey can be damaged by tunneling larvae. Honey production by strong colonies infested with bee lice appears to be little affected. Little work has been done on control of Braula, and the measures that are suggested are antiquated.