Behavioral and chemical analyses of scent-marking in the lek system of a hover-wasp (Vespidae, Stenogastrinae)

Parischnogaster mellyi (Saussure, 1852) males patrol particular hover-sites daily, where they display sex-dimorphic tergal stripes to each other ("stripes display") and where two scent-marking behaviors are likely to occur: first, "oral extrusion" (by males only), where mouthparts are extruded and sex-dimorphic ectal mandibular glands are exposed; second, "spot-marking" (by both sexes), where the tip of the abdomen is applied to the leaf borders, leaving small dark spots after several days. We observed a non-random spatial distribution of stripes displays and scent-marking around the "hotspots" of this aerial lek-like system, regardless of our various lek manipulations. GC-MS analyses of spots on artificial paper leaves revealed the presence of long-chained nonvolatile hydrocarbons that were qualitatively similar to cuticle and hindgut contents of wasps. There were, however, quantitative differences between males and females. We hypothesize a visual-chemical cues system, which presumably plays a role in species-specific and sexual advertising in the forest environment.