CHEMICAL BIOLOGY OF INSECT AND PLANT SIGNALING SYSTEMS
Location: Chemistry Research Unit
Title: Chemical communication in the honey bee scarab pest Oplostomus haroldi: role of (Z)-9-Pentacosene
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 2012
Publication Date: November 14, 2012
Citation: Fombong, A.T., Teal, P.E., Arbogast, R.T., Ndegwa, P.N., Irungu, L.W., Torto, B. 2012. Chemical communication in the honey bee scarab pest Oplostomus haroldi: role of (Z)-9-Pentacosene. Journal of Chemical Ecology. DOI: 10.1007/s10886-012-0211-x.
Interpretive Summary: The Large Hive beetle is a large scarab beetle that attacks bee hives in sub-Saharan Africa. Even a single beetle can cause extensive damage in a honeybee hive and as such it could be a very damaging pest for the apiculture industry in the United States if it were to be introduced into this country. As a consequence it is important to develop monitoring and management strategies for the pest. Scientists from the International Centre of Insect Physiology and Ecology, Nairobi Kenya; The University of Nairobi, Kenya and the Chemistry Unit, Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS in Gainesville Fl. have been studying the reproductive biology of this pest. They documented that mating occurs in the bee hives and identified a sex pheromone, (Z)-9-Pentacosene, from female beetles that is responsible for inducing the close range mating behavior of this pest. The results are the first documentation of a contact sex pheromone produced by a scarab beetle and pave the way to develop methods to inhibit mating using semiochemical based control programs.
Oplostomus haroldi Witte belongs to a unique genus of afro-tropical scarabs that have associations with honey bee colonies, from which they derive vital nutrients. Although the attributes of the honey bee nest impose barriers to communication among nest invaders, this beetle still is able to detect conspecific mates for reproduction. Here, we show, through behavioral studies, that cuticular lipids serve as mate discrimination cues in this beetle. We observed five steps during mating: arrestment, alignment, mounting, and copulation, and a post-copulatory stage, lasting ~40–70% of the total mating duration, that suggested mate guarding. Chemical analysis identified the same nine straight-chain alkanes (C23-C31), six methyl-branched alkanes (6), and five mono-unsaturated alkenes in the cuticular lipids of both sexes. Methyl alkanes constituted the major component (46%) of male cuticular lipids, while mono-unsaturated alkenes were most abundant (53%) in females. (Z)-9-Pentacosene was twice as abundant in females than in males, and ~20 fold more concentrated in beetles than in worker bees. In mating assays, (Z)-9-pentacosene elicited arrestment, alignment, and mounting, but not copulation, by male beetles. These results represent the first evidence of a contact sex pheromone in a scarab beetle. Such contact pheromones may be an essential, cryptic mechanism for arthropods associated with eusocial insects