Alternative male mate-finding tactics in burying beetles

Male burying beetles, Nicrophorus vespilloides Herbst (Coleoptera:Silphidae), use two alternative mate-finding tactics: malescan (1) search for carcasses that serve as oviposition sitesor (2) attract mates via pheromone emission. In the laboratory,all males tested used both tactics, but there were significantdifferences among males in the time they spent employing eithertactic. These differences appear to be partially geneticallybased. Time of day also affected the tactic used. A comparisonof the benefits of the two tactics, based on field and laboratoryexperiments, suggests that the search tactic results in higherreproductive success than the attraction tactic. However, pheromoneemission may be favored toward the end of the activity phase,when female activity is high but carcass availability may belowest. Females readily mate with pheromone-emitting males eventhough this tactic is less profitable than mating with a malethat has already found a carcass. However, it is likely thatfemales can distinguish between males with and without a carcassonly after physical contact. Also, fresh sperm permits femalesto rear offspring if they find a carcass without a conspecificmale.