Both sexes fully winged. Body and legs brown, antennal segment III pedicel paler; major setae brown; fore wings pale, scarcely shaded at base. Antennae 8-segmented; segment III with one sense cone, IV with 4 sense cones, VIII short and broad at base. Head distinctly longer than wide; eyes not prolonged ventrally; postocular setae pointed, almost equal to eye length. Pronotum with no sculpture lines medially, with 5 pairs of pointed major setae; prosternal basantra and ferna present, mesopresternum 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. Currently, 30 species are listed under Leptothrips, all from the Americas. Johansen (1987) described 22 new species in the genus, with 11 Leptothrips recorded from California. However, Mound & O'Donnell (2017) placed nine species into synonymy and recognised only 15 Leptothrips species from North America of which nine are reported from California. Amongst these nine, fasciculatus is one of three species in which females have a small tooth on the inner margin of the fore tarsus; it differs from distalis in lacking duplicated cilia on the fore wings, and from purpuratus, in lacking sculpture lines on the pronotum, and in having a sense cone on the third antennal segment.
Weisenborn (2012) recorded this thrips as anthophilous on Eriogonum fasciculatum [Polygonaceae], with no evidence that it was predatory.
Recorded from California, North Dakota, Oregon, Nevada and Arizona.
Leptothrips fasciculata (Crawford DL)
Phyllothrips fasciculata Crawford DL, 1909: 105
Phyllothrips fasciculata var. stenoceps Crawford DL, 1909: 108
Anthothrips nigricornis Jones, 1912: 17
Haplothrips jonesi Karny, 1912: 344 [replacement name for nigricornis Jones]
Leptothrips russelli Morgan, 1913: 39.
Johansen RM (1987) El genero Leptothrips Hood, 1909 (Thysanoptera: Phlaeothripidae) en el continente Americano: su sistematica, filogenia, biogeografia, biologia, conducta y ecologia. Monografias del Instituto de Biologia. Universidad Nacional de Mexico 3: 1–246.
Mound LA & O’Donnell CA (2017) Predation, phytophagy and character state confusion among North American species of the genus Leptothrips (Thysanoptera: Phlaeothripinae). Zootaxa 4294 (3): 301–315.
Wiesenborn WD (2012) Life stages of the anthophilous thrips Leptothrips fasciculatus (Thysanoptera: Phlaeothripidae). Journal of the Kansas Entomological Society 85: 332–339. https://doi.org/10.2317/0022-8567-85.4.332