Use of contact chemical cues in prey discrimination byCerceris fumipennis

Cerceris fumipennis Say (Hymenoptera: Crabronidae) uses a wide range of adult buprestid beetles to provision nests. Wasps seldom make ‘mistakes’ and attack beetles in other families. Bioassays showed that the wasps use contact chemical cues in the beetles’ epicuticle to discriminate buprestids from other beetles. Wasps rejected buprestids that had their cuticular hydrocarbons (CHC) removed by being washed in solvents. The washed, rejected buprestids became acceptable to 70% of wasps when they were coated with an extract of buprestids’ own CHC. Washed buprestids coated with extracts of non-buprestid beetle CHC were not accepted. Analyses of buprestid CHC profiles showed that they are relatively simple, consisting of five classes. Other coleopteran families that may co-occur in the arboreal hunting habitat of C. fumipennis have a broader range of CHC classes. Experiments adding buprestid hydrocarbons to a non-buprestid beetle, unwashed Popillia japonica Newman (Coleoptera: Scarabaeidae), suggested that wasps may be deterred by the presence of CHC classes not found in Buprestidae. Adding a synthesized dimethyl-branched hydrocarbon, a class of CHC found in Chrysomelidae but not Buprestidae, to the cuticle of unwashed buprestid beetles, caused wasps to reject the buprestid beetles. We propose that CHC act as a kairomone for C. fumipennis, triggering attack, whereas classes of CHC not found in Buprestidae disrupt this response, and thus help to determine the prey range of the wasp.