Body brown, legs yellow, antennae brown with segment III paler; fore wings brown. Antennae 8-segmented, segment III much shorter than IV, both with forked sense cones. Head about as long as wide, projecting weakly in front of eyes; ocellar setae pair I absent, pair III on anterior margins of ocellar triangle; postocular setae in transverse row. Pronotum transverse, with two pairs of posteroangular setae; metanotal median setae arising close to anterior margin. Abdominal tergites without ctenidia, tergite X with a median longitudinal split. Sternites without discal setae; sternite III with pair of pore plates anterolaterally.
Male not known.
Intraspecific variation
Not recorded.
Genus and similar species information
There are 17 species listed in Plesiothrips, mostly light brown to yellowish brown with grey fore wings. All of them live on grasses, and the genus represents a radiation that is unique to the American continent. They all have the ovipositor weak with serrations almost absent, which suggests that they possibly deposit their eggs within grass flowers, rather than into plant tissues. Possibly related to the genus Thrips due to having a similar position of the rudimentary ctenidia on tergites VI & VII, and absence of ocellar setae pair I. Plesiothrips octarthrus is one of three species in the genus with 8-segmented antennae, but unlike P. amblycauda sternite III has a pair of small circular pore plates anterolaterally, and in contrast to P. longicollis there is not a pair of setae in front of the first ocellus. A key to Plesiothrips species is given by Mound et al. (2016).
World distribution
Recorded from Brazil, French Guiana, Panama and Trinidad.
Hood JD (1925) New neotropical Thysanoptera collected by C.B. Williams. Psyche 32: 48–69.
Mound L, Lima E, O’Donnell C, Cavalleri A (2016) New World grass thrips of the genus Plesiothrips (Thysanoptera: Thripidae). Austral Entomology 55: 340–346.
Published in: 30/12/2016 Posted by: Mariana Lindner
