The Order Archaeognatha has previously been combined with the Order Thysanura, or bristletails. Both groups have three-pronged tails with two cerci and an epiproct. Archaeognatha differ from Thysanura in that they are able to use their tail to spring up to 30 cm into the air. Like Thysanura, the body is covered with scales, with a thin exoskeleton that is susceptible to dehydration.