ALTERNATIVE MALE MATE-FINDING TACTICS IN BURYING BEETLES

Male burying beetles, Nicrophorus vespilloides Herbst (Coleoptera: Silphidae), use two alternative mate-finding tactics: males can (1) search for carcasses that serve as oviposition sites or (2) attract mates via pheromone emission. In the laboratory, all males tested used both tactics, but there were significant differences among males in the time they spent employing either tactic. These differences appear to be partially genetically based. Time of day also affected the tactic used. A comparison of the benefits of the two tactics, based on field and laboratory experiments, suggests that the search tactic results in higher reproductive success than the attraction tactic. However, pheromone emission may be favored toward the end of the activity phase, when female activity is high but carcass availability may be lowest. Females readily mate with pheromone-emitting males even though this tactic is less profitable than mating with a male that has already found a carcass. However, it is likely that females can distinguish between males with and without a carcass only after physical contact. Also, fresh sperm permits females to rear offspring if they find a carcass without a conspecific male.