Thrips of Australia

Diagnosis and classification of the Thysanoptera

Thrips differ from other insects in the asymmetry of their mouth parts. The right mandible does not develop beyond the embryo, although the left mandible forms a solid, elongate stylet in larvae and adults. The pair of maxillary stylets (laciniae) are also asymmetric, but these are linked to each other longitudinally by a tongue and groove system. This produces a tube with a sub-apical aperture and one central channel that functions to inject salivary secretions as well as ingest the required food. On each leg, adult and larval thrips have an eversible, adhesive, pretarsal arolium, from which the old name Physapoda (bladder-foot) is derived, but only the larvae retain paired tarsal claws. The modern ordinal name, Thysanoptera (fringe-wings), is derived from the long cilia that border the slender wings of adults, although adults in many species are wingless. The life history of thrips is unlike that of other insects. Following two actively feeding larval stages, there are two non-feeding pupal stages (three among Phlaeothripidae) before the adult is produced. In most flower-living species the pupal stages are found at ground level, but in leaf- and fungus-feeding species they are normally occur on the food substrate. The Order Thysanoptera is considered part of the Hemipteroid complex, the Paraneoptera. But the life history distinguishes the group, and it is best regarded as an exopterygote that has independently adopted holometaboly. Worldwide, nine extant families are currently recognised in the Thysanoptera (also six families of fossil thrips: ThripsWiki, 2020). These families are grouped into two suborders, the Terebrantia and the Tubulifera (Mound et al., 1980; Mound & Morris, 2007; Mound, 2011c). In an alternative classification (Bhatti, 1994, 2006) two Orders are recognised with many small families, but there is no evidence to suggest that most of these groups have any phylogenetic significance (Buckman et al., 2013; Zhang et al., 2019).