Female macroptera. Body typically bicoloured, head and thorax brown but abdomen light brown or yellow with apex dark; legs and antennal segments III–IV yellow; fore wings light brown with basal quarter clear. Antennae 7-segmented; segment I with a pair of small setae dorsally at extreme apex; IV longer than III with apex produced into a neck, both segments with forked sensorium. Head longer than wide, projecting in front of eyes; 2 pairs of ocellar setae present, pair III just in front of hind ocelli and about as long as side of ocellar triangle; postocular setae small. Pronotum with 2 pairs of long posteroangular setae; posterior margin with 2–3 pairs of small setae. Metanotum with little or no sculpture medially, campaniform sensilla absent; median setae small, arising well behind anterior margin. Mesofurca with spinula. Fore wing first vein with 6 setae then a gap to 2 setae near wing apex; second vein with about 10 setae. Tergites with no sculpture medially, usually without ctenidia, but rudimentary ctenidia sometimes present on VI–VII; tergite VIII posterior margin with a few small microtrichia laterally; ovipositor valves very weak, without teeth. Sternites without discal setae, median pair of marginal setae on sternite VII close to margin.
Male macroptera. Similar to female but smaller; antennal segment III very small, IV–VI each with several rings of long setae, VII very small; tergite IX posterior margin with 2 stout thorn-like setae each arising from prominent tubercle; sternites III– IV each with one pair of small circular pore plates placed laterally.
The genus Plesiothrips includes a total of 19 species, all but one from the New World. The presence and position of the rudimentary ctenidia on tergites VI–VII, also the lack of ocellar setae I, suggest that this genus might be related to the genus Thrips. However, the presence of a pair of dorso-apical setae on antennal segment I, and the remarkable sexual dimorphism of the antennae, indicate that Plesiothrips is more likely to be only distantly related to Thrips genus.
Widespread in tropical and subtropical countries.
Queensland, New South Wales, Lord Howe Island.
Feeding and breeding within florets.
Grasses (Poaceae), including sugarcane.
Plesiothrips perplexus (Beach)
Mound LA & Marullo R. 1996. The Thrips of Central and South America: An Introduction. Memoirs on Entomology, International 6: 1-488.