The members of the parainsularis group are characterized by similarities of the male genitalia, female genitalia, and pronotal structure. Externally, the forms appear to be diverse for two reasons: first, the body form of X. parainsularis is narrow while that of X. bisulcifrons is broad; second, the elytra of X. parainsularis are smooth while those of X. bisulcifrons are punctate. The result of these diversities is a superficially different appearance of the two species. Xystosomus parainsularis is similar in appearance to Tachymenis insularis (Darlington) while X. bisulcifrons is similar to a mix of gruti, inflatus, and microtretus group members. However, the male genitalia of the two species in the parainsularis group are very similar and would Venezuela (Figure 71).

Published as part of Erwin, Terry L., 1973, Studies of the subtribe Tachyina (Coleoptera: Carabidae: Bembidiini), Part I: A revision of the Neotropical genus Xystosomus Schaum, pp. 1-39 in Smithsonian Contributions to Zoology 140 on page 26, DOI: 10.5479/si.00810282.140, http://zenodo.org/record/3828531