Tell a Styloperlidae from its wing venation: diagnostic traits of the family derived from a survey of intra-specific variability in Cerconychia livida Klapálek, 1913 and related species (Insecta: Plecoptera)

Abstract

Wing venation is a character system commonly used in the systematics of fossil insects, but the existing documentation for extant forms is often insufficient to allow robust identification of extinct forms. The existing literature suggests that the small stonefly family Styloperlidae Illies, 1966, for which no fossils have ever been identified, might possess a suite of distinctive traits. In order to assess their relevance, we conducted a comparative analysis based on a set of individuals of Cerconychia livida Klapálek, 1913, and of singletons belonging to four additional species. Our survey demonstrates that, in forewing, a fusion of the anterior-most branch of AA2 with AA1 occurs, a trait unique to the family. The occurrence of one to several cross-veins in the distal part of the ScP–RA area (both wing pairs), and of a supernumerary sigmoidal cross-vein in the MP–CuA area (hind wing), are also distinctive features, but are not unique to the family. A few other peculiar traits, which relevance remains unclear, are highlighted. Hopefully, our survey will allow close fossil relatives to be identified in the near future.