Thrips are relatively small, 0.5 to 5 mm long (most are 1 to 2 mm). Wings may be present or absent; and the wings when present are unique among insects because they are narrow, with few or no veins, fringed with long hairs that hence give the order's name, THYSANOPTERA. Mouthparts are piercing-sucking with only a left mandible. Antennae are short (four to nine segments). The tarsi have one or two segments with one or two claws and are bladderlike at the end. They can reproduce sexually or asexually, and females are the most common sex found. Thrips are divided into two suborders, Terebrantia and Tubulifera, that differ in the shape of the last abdominal segment and the development of the ovipositor. The Terebrantia have the last abdominal segment more or less conical or rounded, and the female almost always has a well-developed, sawlike ovipositor. The Tubulifera have the last abdominal segment tubular, and the females lack an ovipositor. The families of thrips are separated largely by the characters of the antennae, particularly the number of antennal segments and the nature of the sensoria on the third and fourth segments. A total of 11 species belonging to two families of two suborders (Phlaeothripidae-Tubulifera, Thripidae-Terebrantia) are included here.
The metamorphosis of thrips is somewhat intermediate between simple and complete. The first two instars are called larvae. In the suborder Terebrantia, these are followed by the third and fourth instars which are inactive, do not feed, and have external wing pads. The third instar is called a prepupa and the fourth the pupa, and are often spent on the ground in soil or litter. In the suborder Tubulifera, the third and fourth instars are prepupae and the fifth pupa. The two sexes of thrips are similar in appearance, but the females are usually larger in size and lighter in color. The thrips with an ovipositor usually lay their eggs in plant tissue; those without an ovipositor lay their eggs in crevices or under bark. Thrips run, crawl, and jump and can move rapidly. Flight is the major method of active dispersal; however, they can be aerially dispersed by drifting in wind currents for many miles.
A great number of thrips are plant feeders. Both larvae and adults feed on flowers, leaves, twigs, or buds, using their piercing-sucking mouthparts, causing structural abnormalities of foliage in the form of leaf malformation (distorted, dwarfed, and matted), leaf fold, leaf roll, leaf blisters, and sometimes defoliation; causing discoloration of petals, deformation, or scarring of flowers. A few species feed on fungus spores, a few species are predaceous on other small arthropods (mites, thrips, and aphids) and a few species may bite man. A very important aspect of thrips is the transmission of virus diseases. Tomato spotted wilt virus, is transmitted by the western flower thrips, tobacco thrips, and onion thrips.