Barolineocerus chiasmus is a species of leafhopper in the family Cicadellidae, subfamily Eurymelinae, tribe Chiasmodolini. It was described by Paul H. Freytag in 2008.
Distribution: The species is native to French Guiana. The type locality is 33 km southeast of Roura on Kaw Road, Roura, French Guiana.
Description: Adults measure 4.0–4.3 millimeters (0.16–0.17 in) in length. The species is named for a thin, sword-like protrusion (a chiasma-like structure) on the last segment of the abdomen of the male. This protrusion is the primary characteristic used to distinguish B. chiasmus from other species within the genus Barolineocerus.
Taxonomy: The species belongs to the genus Barolineocerus, which was also established by Freytag in 2008. Members of this genus are Neotropical leafhoppers ranging from 4–6 mm in length, with yellow to white heads, brown-margined faces, and yellow to yellow-green wings.
Related species: Barolineocerus chiasmus shares characteristics with B. ornatus, B. chicomendesi, B. dercyae, and B. digitatus, particularly in having a pair of elongate median processes on the posterior margin of the pygofer and subgenital plates that are rounded apically.
Reference: Freytag, Paul H. (January 2008). "Two new genera of Idiocerinae (Hemiptera: Cicadeillidae) from South America, including the description of ten new species". Entomological News. 119 (1): 47–60.
