Crickets (also known as "true crickets"), of the family Gryllidae, are insects related to bush crickets, and, more distantly, to grasshoppers. The Gryllidae have mainly cylindrical bodies, round heads and long antennae. Behind the head is a smooth, robust pronotum. The abdomen ends in a pair of long cerci (spikes); females have a long cylindrical ovipositor. The hind legs have enlarged femora (thighs), providing power for jumping. The front wings are adapted as tough, leathery elytra (wing covers) and it is by rubbing parts of these together that some crickets chirp. The hind wings are membranous and folded when not in use for flight; many species however are flightless. The largest members of the family are the bull crickets, Brachytrupes, which are up to long.