Horistothrips Morgan

(Fig. 66)

Horistothrips Morgan, 1913: 36 . Type species: Horistothrips australiae Morgan, by monotypy. Three of the five species listed in this genus, two from Fiji and one from Zhejiang, China, are possibly not congeneric with the two species from Australia, including the type species (Mound 2008). The antennal sensorium formula of H. australiae (1 on segment III and 3 on IV) places this species in association with the leaf-feeding species of the Liothrips -lineage (following couplet 35). However, it is known to be a fungus-feeder on the bark of trees (Tree & Walter 2012). Therefore it seems that either this Australian thrips has undergone a reduction in the number of sensoria, or else that it has reverted from leaf-feeding to fungus-feeding.

Diagnosis: Usually micropterous; head longer than wide, posterior half reticulate; postocular setae capitate; stylets retracted to eyes, close together medially (Fig. 66); antennae 8-segmented, VIII broad at base, III with 1 sensorium, IV with 3 (or 2) sensoria; pronotum with 5 pairs of capitate setae, notopleural sutures complete; basantra absent; mesopresternum reduced to two lateral triangles; sternopleural sutures long; both sexes with fore tarsal tooth; pelta triangular; tergites II–VII each with 2 pairs of wing-retaining setae; tube shorter than head, anal setae much longer than tube; male sternite VIII with large pore plate.