An order of wingless insects with soft, fusiform bodies 0.12–0.8 in. (3–20 mm) long, often covered with flat scales forming diverse patterns. The mouthparts are free with dicondylous mandibles used for scraping and chewing. Antennae are long and threadlike (filiform) with muscles present only in the scape and pedicel. Visual organs may be a cluster of simple ommatidia (cylinder-shaped units of a compound eye) or lacking altogether. The abdomen terminates in three “tails”: a pair of lateral cerci and a median caudal filament (telson). Females have well-developed ovipositors; males have a penis and often one or rarely two pairs of parameres.