Both sexes fully winged. Body and legs brown, antennal segment III pedicel paler; major setae brown; fore wings pale, scarcely shaded at base. Head distinctly longer than wide; eyes not prolonged ventrally; postocular setae pointed, almost equal to eye length. Antennae 8-segmented; segment III with one sensorium, IV with four sensoria, VIII short and broad at base. Pronotum with 5 pairs of pointed major setae; prosternal basantra and ferna present, mesopraesternum reduced to paired lateral triangles. Fore tarsus with small pointed tooth. Metanotum closely striate medially. Fore wing constricted medially, without duplicated cilia. Tergite IX setae S1 pointed, as long as tube.
Male similar to female, but fore tarsal tooth larger; tergite IX setae S2 short and stout; sternite VIII with no pore plate; pseudovirga of aedeagus slender.
The genus Leptothrips is related to Haplothrips, but the metanotal sculpture is closely striate not reticulate, and larvae and adults usually have extensive purple internal pigment. In total, 38 species are listed under Leptothrips, all from the Americas. Johansen (1987), in describing 22 of these as new species, recorded 11 Leptothrips from California, although only seven were listed by Hoddle et al. (2004). The validity of some of the species in the genus remains questionable, as discussed here under L. mali. The problem is that many of these species were differentiated on character states that are very difficult to observe on their type specimens because these are poor quality slide-mounts. Moreover, there is little recorded habitat segregation between several of the nominal species, given that they are all considered to be predators of other arthropods.
Leptothrips fasciculatus (Crawford DL)
Presumably predatory on small arthropods living on desert shrubs
Associated with Eriogonum fasciculatum (Polygonaceae).
California, North Dakota, Oregon, Arizona.