Rattailed Maggots
Drone fly, Eristalis tenax (Linnaeus), and Eristalinus aenus (Scopoli),
Syrphidae, DIPTERA


Adult -- The drone fly or rattailed maggot resembles the honey bee in action and appearance but has only one pair of wings. Its body is brownish to black, fairly hairy and about 15 mm long. The thorax has a yellowish tint and a vertical stripe. Eristalinus aeneus resembles a dark, greenish, metallic blow fly (bottle fly), but Eristalinus aeneus has stripes on the thorax.

Egg -- Each white, elongate-oval egg is usually less than 1 mm long.

Larva -- The larva of these flies are aquatic, rattailed maggots. The cylindrical, grub-like body may be up to 20 mm long with a tail-like breathing tube 30 to 40 mm long. This hard-bodied life stage i s resistant to crushing. The species of rattailed maggots are difficult to determine in the larval stage.

Pupa -- Enclosed in the hardened skin of the last larval instar, the pupa appears a little shorter and fatter than the mature larva.


Distribution -- These flies occur throughout much of the world. The drone fly was introduced into North America sometime prior to 1874. Both flies are now common from Alaska to Labrador and south into California and Florida.

Feeding Habits -- These flies are attracted by colorful flowers (especially yellow) as well as by odors of decay. They do not suck blood. Rattailed maggots feed on decaying organic matter in stagnant water or moist excrement.

Damage -- Rattailed maggots are very rarely pests. Occasionally larvae appear in alarming numbers in dung pits or animal waste lagoons. Even so, they pose little threat to man or animals. However, a few rare cases of entericpseudomyiasis (intestinal infestation by fly larvae) have been caused by this species.

Life History -- Drone flies have an unusual and little-studied life cycle. The female fly lays 4 or 5 eggs on or near contaminated water, sewage or other decaying organic matter. The larvae which hatch from these eggs are reported to reproduce paedogenetically, that is, each one gives rise to 7 to 30 daughter larvae. This method of reproduction may last for some time, but periodically female and male flies are also produced. Larvae can withstand many adverse conditions but are eaten by other fly larvae, particularly those of the genera Ophyra, Muscina, Phaonia, etc. Pupation usually occurs in a site drier than that in which the larvae developed. The number of annual generations produced is unknown.


Drone flies have never been implicated as disease vectors and usually do not become a problem if sewage and manure are not allowed to accumulate in pits, ponds, or streams. Chemical control is rarely necessary.