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Thrips of California 2012

Thysanoptera biology

All Thysanoptera species have two larval instars that feed actively. Species in the suborder Tubulifera then have three pupal instars, whereas species in the suborder Terebrantia have only two pupal instars before emerging as adults. In some species, pupae are found together with larvae and adults, but in many species, mature larvae fall to the ground or crawl into crevices in order to pupate. The second instar larvae of species in the Aeolothripidae, Melanthripidae and Heterothripidae secrete, or weave, a translucent cocoon in which to pupate, and an account of this in one species is given by Hoddle et al. (2000, 2001). Pupal cocoons are also produced by a few Thripidae, such as species of Odontothrips.

The larvae of most species of Terebrantia live and feed on leaves or in flowers, and although some species feed in both of these sites, other species are specific to either leaves or flowers with only stray individuals being found out of context. Heliothrips haemorrhoidalis, the Greenhouse Thrips, will feed on a remarkably wide range of plant species, but is particularly associated with old leaves and is most abundant on plants that are under stress. In contrast, species related to Dendrothrips live on young leaves, but although this is true also of Scirtothrips species, adults of these may at times be found in flowers. Several Thripidae are predatory on other small arthropods, a few such as Scolothrips species are obligate predators, others such as Thrips tabaci and Frankliniella occidentalis are facultative predators and feed on both plant and arthropod tissues. Among the Aeolothripidae, the predatory habit seems more common, but again, more species appear to be facultative predators within flowers rather than obligate predators on leaves or at ground level.

In the Phlaeothripidae, only a few species feed and breed in flowers. In almost 50% of the species, the larvae and adults feed only on fungus, the Idolothripinae on spores and the Phlaeothripinae on hyphae, and in almost 50% of species the larvae feed on green leaves. Fungus-feeding Phlaeothripidae are known to exhibit interesting competitive behavior between males (Crespi, 1986, 1988), and leaf-feeding members of this family sometimes induce galls (Crespi et al., 2004).