Wings folded. The halteres are the stubs behind the wings. Except for Flies (Diptera), all flying insects have two sets of wings. In flies, the back wings have been reduced to nubs -- the halteres. "Flies are the most accomplished fliers on the planet in terms of aerodynamics... They can do things no other animal can, like land on ceilings or inclined surfaces... And they are especially deft at takeoffs and landings -- their skill far exceeds that of any other insect or bird.'' (Michael Dickinson, UC Berkeley, quoted at <http://www.flypower.com/facts.html>) This is made possible by the halteres. This web site says that the halteres are hard-wired to the fly's eyes, giving rapid feedback in flight.