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Chemically-mediating mate recogntion in the longhorned beetles (Coleoptera: Cerambycidae).
Ginzel, Matthew*,1, Millar, Jocelyn2, Hanks, Lawrence 1, 1 University of Illinois at Urbana-Champaign, Urbana, IL2 University of California - Riverside, Riverside, CA
ABSTRACT- The wax layer on the cuticle of insects is comprised of a complex mixture of long-chain fatty acids, alcohols, esters, aldehydes, ketones, and hydrocarbons that protect insects from desiccation. Components of the wax layer also may have a secondary role as contact pheromones. There is a growing body of evidence that mate recognition in cerambycid beetles is mediated by such contact sex pheromones. We add to our previous work on cuticular hydrocarbons of cerambycids and indentify the contact pheromone of the locust borer Megacyllene robiniae (Forster). Male M. robiniae respond to females only after touching them with their antennae, indicating that mate recognition is mediated by a contact sex pheromone. GC-MS analyses of whole-body extracts revealed compounds present in the wax layer of females that are absent or present in smaller quantities in males. We reconstructed blends of the most abundant female specific straight-chain (nC23, nC24, nC25, nC26), methyl-branched (3me-C23, 3me-C25), and unsaturated (Z9:C23, Z9:C25, Z9:C27) compounds and assessed their bioactivity in arena bioassays. In these bioassays, males showed the greatest response to Z9:C25 alone. This compound elicited the complete sequence of mating behaviors, up to and including coupling the genitalia. Z9:C25 comprised 16.4 ± 1.3% of the total hydrocarbons while in solid phase microextraction wipe samples of the cuticle, Z9:C25 comprising 34.6-38.3% of the sampled hydrocarbons. Our data indicate that Z9:C25 is the contact sex pheromone of M. robiniae, being the most abundant hydrocarbon on the cuticular surface of females where it is readily accessible to the antennae of males.
Key words: contact pheromone, mate recongition , cuticular hydrocarbons