Freeloading flies go legless and wingless.

Even moochers must make some sacrifices. Adult children living at home, for example, often must follow their parents' antiquated rules or risk being booted out. But if hosts' regulations seem intolerable, consider the plight of the legless scuttle fly, which scientists recently discovered in Malaysia.

In order to live in the nests of Aenictus ants, the female flies develop neither wings nor legs-that way they resemble ant larvae, the researchers report. These flies, members of the Phoridae family, have apparently convinced the normally fierce, predatory ants to feed and care for them, say Andreas Weissflog of the Johann Wolfgang Goethe University in Frankfurt, Germany, and his colleagues.

Male flies, which have wings, probably carry the females to the ant nests after mating, says coauthor R. Henry L. Disney of the University of Cambridge in England.

Until they have completed a detailed study, the researchers can only speculate on the insects' interaction. Disney will assign the fly a scientific name and further describe it in an upcoming Sociobiology.

Researchers had known that insects often reside in other species' nests, using unique disguises and survival strategies. A number of species shed their wings, and some flies release a chemical that placates their termite hosts when the termites lick it, explains Disney.

"Many aberrant insects are known from colonies of social insects but few as bizarre as that reported here," the authors assert in the Nov. 9 Nature.

"The reason [the legless scuttle fly] is unusual is the high level of structural modification it has undergone," says Donald H. Feener Jr. of the University of Utah in Salt Lake City. Also, the fly is surprisingly dependent, Disney adds.

The flies were probably born without wings or legs, as they lack the musculature to support either, the authors observe. However, the insects have microscopic wicks that probably dispense a pheromone with an antlike odor.

The discovery of this freeloading fly will help scientists understand how insects get around each other's communication and defense systems, Feener notes.