Adult Reproductive Behavior

Recognition of beetles of the same species as mates is important, as beetles are frequently present in large numbers in fresh dung. Male beetles court females by tapping them with their head and forelegs prior to successful copulation. The males of many species produce pheromones that are probably involved in close-range species recognition and in sexual attraction. Pheromones are released via pumping movements from forelegs, or from abdominal sternites, depending on the species.

Male-to-male intraspecific competition occurs in tunnels in the soil for the possession of a female making a brood mass where she is to lay her egg. Of the two males, the larger is usually successful in pushing the smaller beetle away from the

FIGURE 4 A pair of K. nigroaeneus rolling a brood ball. The female sits on the ball while the male rolls it backward (beetles approx 2 cm in length). (Reproduced, with permission, from Edwards and Aschenborn, 1988.)

tunnel and the female. This behavior is widely reported in species in both the larger genera such as Scarabaeus, Kheper, and Typhoeus, and the smaller genera such as Onthophagus. The size of male beetles and of horns arising from their head, thorax, and clypeus can be very variable. In many of the smaller species, beetles exhibit dimorphic male morphology. Both large horned major and small hornless minor morphs (forms) coexist in the field. Females produce more brood masses, and the brood masses are larger, in the presence of horned males than in the presence of hornless males. Offspring size is determined by the size of the brood mass used to provision the larva. The horned males assist the females in dung provisioning, providing each egg with more dung. They also guard the tunnels where the females are producing brood masses from other males. The hornless males show alternative mating strategies, by sneak mating with unguarded females, but they do not assist the females in providing dung for brood masses after mating.

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