Effects of Size and Flight Performance on Intermale Mate Competition in the Cicada Killer, Sphecius speciosus Drury (Hymenoptera: Sphecidae)

The characteristics of successfully mating male cicada killers (Sphecius speciosus Drury) were compared to those of unsuccessful males. In the field, successful males were larger and had higher ratios of flight muscle mass to body mass (flight muscle ratios) than unsuccessful males. The elevated flight muscle ratio of successful males was not because of semen transfer to the female nor because of an allometric effect. Better territory-holding ability and flight maneuverability probably contribute to the success of large males with a high flight muscle ratio in nature under most conditions. However, temporal or situational conditions may also exist whereby small males may occasionally have opportunities to mate.