Olfactory cues in the host-location of the European ecto-parasitoids Sclerodermus cereicollis and Sclerodermus domesticus (Hymenoptera: Bethylidae)

Chemical ecology regarding the flat wasps of the genus Sclerodermus is poorly known and deserves further attention in order to improve the efficacy of these bethylid species as biological control agents against xylophagous insects and stored product insect pests. In the present investigation the host location process of S. cereicollis and S. domesticus, ectoparasitoids attacking xylophagous insects infesting decaying or dead or worked wood, has been studied. Bioassays in Y-tube olfactometer, still air olfactometer and open arena have been performed. Females of both species, in agreement with the typical behaviour of generalist parasitoids, revealed to be able to perceive and respond to different volatile chemicals produced by the host habitat (seasoned-wood sawdust from pine and beech) and host frass of the two longhorn beetles Hylotrupes bajulus and Trichoferus holosericeus. In addition, they can perceive non-volatile chemicals from the host cuticle (cuticular hydrocarbons of the two longhorn beetles). The two species revealed numerous similarities and some differences in their behaviour. Such differences highlight the importance of clarifying the chemical ecology of the different species of the genus Sclerodermus a taxon in which the taxonomy and biology of the different species are still unclear.