Differences in mating tactics performed by males of two local populations of the Japanese scorpionfly Panorpa japonica

Males of the Japanese scorpionfly, Panorpa japonica, often perform male–male competitions for food to offer to females as a nuptial gift. Previous studies have suggested that the behavior of males who lost in male–male competition (loser male) differs between two geographically separated populations. In the Aichi population, loser males wait around the feeding area and attempt forced mating with females as “satellites” (Thornhill, Anim Behav 44:867–879, 1992a), while in the Okayama population, loser males frequently try to re-enter the feeding area as “sneakers”, and the loser males who succeed in sneaking attempt to mate with present females (Ishihara and Miyatake, J Ethol 39:267–274, 2021). However, these two studies were conducted about 30 years apart, and many factors may have changed since that time. Therefore, in the present study, mating behaviors of the two populations were compared within the same year by field observations. Our results showed that most of the individuals in the Okayama population stayed near their feeding grounds longer on average than the Aichi population while repeatedly snaking. On the other hand, in the Aichi population, more individuals left the feeding area than those who chose sneaking. In addition, the number of females visiting the feeding area was significantly higher in the Okayama population. Results of a laboratory experiment using males from two local populations showed that the behavior of loser males was similar to field observations. These findings suggest that males from the two populations adopt alternative mating tactics. We discuss the reasons why the populations show different mating tactics.