Thysanoptera comprise 4,500 species in nine families and two suborders (Terebrantia and Tubulifera) and constitute the sister group of the Hemiptera. Larvae and adults feed on the mycelia, spores, or digestive products of fungi; on algal cells; on the leaves, flower parts, stems, fruits, seeds, nectar, or pollen (but not vascular tissues) of higher plants; or on other small arthropods. They do so by use of asymmetric, punch-and-suck mouthparts arranged in a cone below the head which consists of the labrum, maxillary stipites, and labium, bears paired maxillary and labial palpi, and contains the left mandibular stylet, two maxillary stylets (laciniae), and cibarial and salivary pumps. Before feeding, a thrips punches the substrate with its mandible and protracts its laciniae into the resulting hole through a labral ring. On their protraction, the laciniae fit together along their lengths to form a feeding tube with a subterminal opening. Action of the cibarial pump draws food into this tube and that of the salivary pump propels saliva out through the same canal but at different times. Although similar throughout the order, the mouthparts of terebrantians and tubuliferans differ in mouthcone mobility, in labral structure, in extent of the clypeo-labral membrane, in mode of mandibular protraction, in relative length and articulation of the laciniae, in mode of cibarial pumping, and in the details of their sensilla, molting, and metamorphosis. The ontogeny of the mouthparts is considered, and their evolutionary origin is addressed in the light of fossil and phylogenetic evidence. The latter suggests that thrips originated in Upper Carboniferous litter from a psocopteroid stem species that fed on fungus. This life style is retained by extant uzelothripids, merothripids, and lonchothripids and by many phlaeothripids. Members of the phlaeothripid subfamily Idolothripinae ingest whole spores using broad, bandlike laciniae. Phytophagy has evolved independently in thripids and phlaeothripids. Pollenophagy (aeolothripids, adiheterothripids, fauriellids, heterothripids, thripids, phlaeothripids) and predation (aeolothripids, thripids, phlaeothripids) have each evolved independently three and probably more times within the Thysanoptera.