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

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