Insects of this order are commonly known as thrips, and the name Thysanoptera comes from the Greek 'thysanos' meaning fringe, and 'pteros' meaning wing, referring to the slender wings that bear a dense fringe of long hairs. There are about 5,000 described species, in 6 families. These are small insects (usually between 0.5 to 3.0 mm long), found in tropical and temperate regions of the world. Thrips are the only insects with asymmetrical mouthparts; they have only the left mandible, while the right one disappears during embryogenesis. Adults may be winged or wingless, and both young and adults have eversible, adhesive arolia on each leg. They are hemimetabolous insects; following two actively feeding nymphal stages, there are two or three non-feeding pupa-like instars before the adult arises. Thrips are commonly found in flowers, leaf litter, moss and fungi. Almost half of the known species of thrips feed only on fungi, an appreciable number feed only on green leaf tissues, and a few are predators of mites and other arthropods. Females of the suborder Terebrantia possess an ovipositor used to cut slits into plant tissue into which they insert their eggs, while those of the suborder Tubulifera lack an ovipositor and lay their eggs on the plant surface. Many Thrips are pests of commercial crops, fruits, and garden flowers, due to the direct feeding damage they cause, gall formation or virus diseases they transmit.