Sting morphology and frequency of sting autotomy among medically important vespids (Hymenoptera: Vespidae) and the honey bee (Hymenoptera: Apidae).

Abstract

Data from clinical sting challenge investigations indicate that certain species of yellowjackets experience sting apparatus autotomy with surprisingly high frequency. However, a retrospective survey of vespid collectors strongly supports the supposition that the frequency of yellowjacket sting autotomy seen in clinical situations is not representative of the frequency experienced under field conditions. Examination by electron microscopy of the sting apparatuses of several vespid species and that of Apis mellifera L., the honey bee, revealed previously unreported structural variations between apid and vespid aculei which likely contribute to differences in sting autotomy rates observed between the honey bee and the social wasps. Specifically, when the lancets of a vespid aculeus are in a retracted position, the width of the smooth-edged stylet extends beyond the barbed edges of the lancets, forming a protective sheath. By contrast, all honey bee aculei possess stylets of insufficient width to shroud the barbs of retracted lancets, thus allowing the barbs to be completely exposed. Additionally, the dorsal surface of all vespid stylets are smooth in contrast to the dorsal surface of honey bee stylets, which support from one to three rows of paired barbs. The exposure of barbs on retracted honey bee lancets and the presence of additional barbs on the dorsal tip of the stylet would make withdrawal of a honey bee aculeus from a victim's flesh more difficult than withdrawal of a vespid aculeus, in which the barbs of retracted lancets are shielded and no dorsal barbs are present.