A new long-winged pygmy grasshopper in Eocene Baltic amber raises questions about the evolution of reduced tegmenula in Tetrigidae (Orthoptera)

Abstract

Extant pygmy grasshoppers (Tetrigidae) that possess wings have the forewings reduced into scale-like tegmenula, while hind wings remain fully developed. Rusmithia gorochovi gen. et sp. nov. (Tetrigidae, Batrachideinae, Rusmithini trib. nov.) is described based on a single adult female holotype from Lithuanian Baltic amber, from the Bartonian-Priabonian age, some 40 million years ago, and this is the only known tetrigid in which tegmenula or tegmina (the forewings) extend as far as half the length of the hind femur. Besides this very unique trait, other characters of Rusmithia gen. nov. indicate similarity with extant and especially fossil Batrachideinae (genus Danatettix Thomas, Skejo & Heads, 2019). Because of the strong differences this genus and Danatettix have with American Batrachideinae, they are assigned to a new tribe, European Batrachideinae or Rusmithini trib. nov. Acrydium bachofeni (Zeuner, 1937) might belong to this or a sibling genus based on its very long tegmenula or Succinotettix chopardi Piton, 1938, based on its 19-segmented antennae; neither species is tranferred as their types could not be examined.