DISCOVERY THROUGH DIGITIZATION: A NEW SCENTLESS PLANT BUG (FAMILY: RHOPALIDAE) FROM THE NEOGENE STEWART VALLEY, NEVADA, USA

A new scentless plant bug (Rhopalidae) from the mid-Miocene of Nevada (SV) was discovered while imaging the Stewart Valley insects for the Berkeley Fossil Insect PEN digitization project. The SV represents a well-dated basin that started forming ~17 Mya and preserves one of the most complete terrestrial paleoecosystems known from the Neogene of North America. Harvey Scudder provided a list of 14 Orders and 40 Families in a 1986 survey of the insects, but to date only a snakefly, honey bee, and crane fly have been formally described.

Here, we recognize 11 specimens as a new species of rhopalid previously identified by Scudder as a mirid (Miridae). The specimens come from the lacustrine “paper shales” of the Savage Canyon FM dated at ~14.5 Ma. The body is an elongate oval shape, dark, punctate, with an average length of 6.94 mm. The head is broad, terminal antennal segments are clubbed, the pronotum lacks an anterior collar, a punctuate area occurs in front of its cicatrices, the metasternum is grooved for beak entry and the beak does not extend beyond the metasternum, if the latter is interpreted correctly. Based on this combination of characters and others, the fossils are morphologically most similar to species in the subfamily Rhopalinae, tribe Rhopalini and shares most characters with the genera Rhopalus and Brachycarenus. The most distinctive feature of the SV fossils, however, is the light-colored “figure-8” on the abdomen below which is a series of two semi-circular-shaped markings. This pattern is nearly identical to extant Brachycarenus tigrinus, a species closely related to Rhopalus. Both Rhopalus and Brachycarenus are considered Palaearctic endemics, and B. tigrinus is a species recently introduced into the US. Presence of the SV rhopalid suggests a Rhopalus/Brachycarenus-like insect in western NA (Nearctic) ~14.5 Mya and raises questions regarding the origin and biogeographic history of these two genera.