Generic diagnosis

Small pale or bicoloured, macropterous or micropterous Phlaeothripinae with unusually long maxillary stylets. Head little longer than wide; postocular setae small and capitate, arising behind inner margin of compound eyes; maxillary stylets deeply retracted into the head, close together or crossing over in middle of head, with one or more convolutions near base of head; mouth cone rather long. Antennae 8-segmented; VI broadly truncate at apex, VII not narrowed at base; III with no sense cones (rarely with 1), IV with 2 ventral sense cones. Pronotal major setae all present, small with expanded apices; notopleural sutures complete. Prosternal basantra absent, mesopresternum present or absent; metathoracic sternopleural sutures long and curved. Mesonotal midlateral setae very small, apex expanded. Metanotum with several pairs of small setae. Fore tarsal tooth present in female, usually present in male; fore tibia with an apical tubercle in two species. Fore wings evenly wide, without duplicated cilia; 3 short sub-basal setae present with expanded apices. Pelta broadly triangular with lateral margins eroded; tergites II–VII usually with 2 pairs of sigmoid wing-retaining setae; tergal posteromarginal setae S1 broadly expanded, arising very close to wing-retaining setae; posteroangular seta small on tergites II–VI; tergite IX setae S1 and S2 short and expanded, S3 acute; tube shorter than head, sometimes strongly reticulate and expanded. Male sternite VIII with no pore plate, but median sternites sometimes with transverse band of specialised reticulation.

Nomenclatural data

Adrothrips Moulton, 1942: 4. Type species Adrothrips aureus Moulton 1942, by monotypy.

The five described species in this genus are all from Australia; further species are known and await description.

Australian species
Adrothrips akanthus Mound, 1970: 446
Adrothrips aureus Moulton, 1942: 5
Adrothrips cotteri Mound, 1970: 444
Adrothrips intermedius (Bianchi, 1945: 254)
Adrothrips systenus Mound, 1970: 451

Relationship data

This genus is unusual in the absence of sense cones from the third antennal segment in all but one of the included species, and in three of the five species the form of the last abdominal segment is unique. The broad truncate apex to antennal segment VI is shared with members of the Rhopalothripoides genus group, as is the absence of a sense cone on antennal segment III.

Distribution data

This is an Australian endemic genus that is known mainly from semi-arid areas in the eastern part of the continent. However, A. intermedius is widespread in Australia on Casuarina cunninghamiana but was described originally from New Caledonia.

Biological data

All species of this genus live and breed on various species of Allocasuarina and Casuarina. Some of these species have unusually elongate maxillary stylets, and these presumably feed on the tissues of the green branchlets using the long stylets to reach the living cells that are in a groove and protected by sclerenchym cells. However, one species with shorter stylets has been found breeding in a woody gall, and this habit may be shared by a few other members of the genus. The extraordinary form of the tenth abdominal segement in females of some species is reminiscent of the structure in Dactylothrips species, and may be associated with repelling marauding ants.

References

Mound LA (1970) Convoluted maxillary stylets and the systematics of some Phlaeothripine Thysanoptera from Casuarina trees in Australia. Australian Journal of Zoology 18: 439–463.