were itinerant vendors of such materials, but a connection between these words and the insects has not been established. Evolution and phylogeny Fossil history Fossil caddisflies have been found in rocks dating back to the Triassic. The largest numbers of fossilised remains are those of larval cases, which are made of durable materials that preserve well. Body fossils of caddisflies are extremely rare, the oldest being from the Early and Middle Triassic, some 230 million years ago, and wings are another source of fossils. The evolution of the group to one with fully aquatic larvae seems to have taken place sometime during the Triassic. The finding of fossils resembling caddisfly larval cases in marine deposits in Brazil may push back the origins of the order to the Early Permian period. Evolution Nearly all adult caddisflies are terrestrial, but their larvae and pupae are aquatic. They share this characteristic with several distantly-related groups, namely the dragonflies, mayflies, stoneflies, alderflies and lacewings. The ancestors of all these groups were terrestrial, with open tracheal systems, convergently evolving different types of gills for their aquatic larvae as they took to the water to avoid predation. Caddisflies was the only group of these insects to use silk as part of their lifestyle, which has been a contributing factor to their success and why they are the most species-rich order of aquatic insects. About 14,500 species of caddisfly in 45 families have been recognised worldwide, but many more species remain to be described. Most can be divided into the suborders Integripalpia and Annulipalpia on the basis of the adult mouthparts. The characteristics of adults depend on the palps, wing venation and genitalia of both sexes. The latter two characters have undergone such extensive differentiation among the different superfamilies that the differences between the suborders is not clear-cut. The larvae of Annulipalpians are campodeiform (free-living, well sclerotized, long legged predators with dorso-ventrally flattened bodies and protruding mouthparts). The larvae of Integripalpians are polypod (poorly sclerotized detritivores, with abdominal prolegs in addition to thoracic legs, living permanently in tight-fitting cases). The affinities of the third suborder, Spicipalpia, are unclear; the larvae are free-living with no cases, instead creating net-like traps from silk. Phylogeny The cladogram of external relationships, based on a 2008 DNA and protein analysis, shows the order as a clade, sister to the Lepidoptera, and more distantly related to the Diptera (true flies) and Mecoptera (scorpionflies).