Sting microsculpture in the digger wasp Bembix rostrata (Hymenoptera, Crabronidae)

Abstract

Th e sting microsculpture of the digger wasp Bembix rostrata (Fabricius, 1781) (Hymenoptera, Crabronidae) is studied with the scanning electron microscope (SEM) for the fi rst time. As in many other hymenopterans, the second valvifer of B. rostrata possesses two fi elds of styloconic sensilla (hair plates) of proprioceptive function. Th e presence of two paired fiof campaniform sensilla on the second valvula and second valvifer is fi rst shown in an apoid wasp. Th e fi rst and the second valvulae bear scattered sensilla-like structures on the external surface, more numerous apically. Th e fi rst valvula has two subapical barbs externally and a pair of valvilli on its inner surface, whereas the outer surface of the second valvula is smooth. Th e third valvula is sclerotized externally, consisting of proximal and distal parts, and bearing four sensilla morphotypes of mechanoreceptive and probably chemoreceptive functions. Th e inner surface of the valvulae and the membranous cuticle that is touching the sting have microstructures of diff erent shapes directed distally. Functional aspects of characters studied are discussed.