Pterygote insects are primarily winged; the meso-and metathoracic segments are usually large and united to form the pterothorax, from which the wings arise (one pair of wings from each of the segments). The wings are veined. In some taxa they have been secondarily lost or modified into specialized structures like wing covers (elytra, e.g. in Coleoptera) or flight balancers (halteres, e.g. in Diptera).
Moulting occurs only in the immature stages. There are 8-11 abdominal segments, with the genital pore situated on segment 8 (females) or 9 (males). The pregenital segments lack appendages but the genitalia vary in their morphology according to the mating habits of the species. Fertilisation is internal, involving copulation, with the male intromitting either sperm or a spermatophore directly into the female reproductive tract. The sexes are usually separate (dioecious) but asexual reproduction by parthenogenetic females is common in some taxa.