Thrips are small and slender insects, with the adults of British species ranging from 1.0-7.0 mm in length. Winged thrips are easily recognised by the combination of basic body shape and presence of four narrow wings each with a long fringe of marginal cilia. However, the possession of such a marginal wing fringe is not unique to thrips, although it gives the Order its name ("Thysanoptera" = fringe-wing).
Formally, therefore, the Thysanoptera comprises a single Order in which the members differ from all other insects in the form of the mouth parts and the tarsal arolium. The mouth parts are asymmetric, with only the left mandible functional in larvae and adults, the right being resorbed in the embryo. The two maxillary stylets are co-adapted to form a single tube through which salivary secretions are pumped out and partially digested cell contents are pumped back into the thrips foregut (Heming, 1993). Larval thrips retain tarsal claws, but these are replaced in adults by an inflatable arolium (Heming, 1971) that functions in a similar way to the pulvilli of dipterous flies.
This Order represents one of the four major divisions of the Paraneoptera or Acercaria, the Hemipteroid group that also includes the Hemiptera, Phthiraptera and Psocoptera (Heming, 2003). Among these Orders, the Thysanoptera is considered to be sister-group to the Hemiptera (Grimaldi & Engel, 2005). However, a fifth Order of Acercaria has also been proposed, the Permopsocida from mid-Cretaceous Burmese amber, as sister-group to Hemiptera and Thysanoptera. This Order of fossil insects represents the earliest example of the suctorial mouth-parts that distinguish thrips and bugs from all other insect groups (Huang et al., 2016).
Grimaldi DA & Engel MS (2005) Evolution of the Insects. Cambridge: Cambridge University Press.
Heming BS (1971) Functional morphology of the thysanopteran pretarsus. Canadian Journal of Zoology 49: 91-108.
Heming BS (1993) Structure, function, ontogeny, and evolution of feeding in thrips (Thysanoptera). pp. 3-41 In Schaefer CS & Leschen RAB (eds). Functional Morphology of Insect Feeding. Thomas Say Publications in Entomology. Entomological Society of America. Lanham, MD.
Heming BS (2003) Insect Development and Evolution. Cornell University Press.
Huang DY, Bechly G, Nel P, Engel MS, Prokop J, Azar D, Cai CY, Kamp T van de, Staniczek AH, Garrouste R, Krogmann L, Santo Rolo T, Baumbach Y, Ohlhoff R, Schmakov AS, Bourgoin T & Nel A (2016) New fossil insect order Permopsocida elucidates major radiation and evolution of suction feeding in hemimetabolous insects (Hexapoda: Acercaria). Nature Scientific Reports 6:23001. DOI: 10.1038/srep23004