Abstract
• Swarming and mating behaviors of a mayfly species, Ephemera orientalis Mclachlan, 1875 were observed in 2015, 2016, and 2018 at a river bank of the Asahi River, Japan. • Males started to make swarms between late April and middle May in 2016 and 2018. • Swarms were formed during a limited period at dusk most probably because that interval is free from natural enemies, and males competed with each other to copulate with females in swarms. • We also clarified the function of the forelegs of males, which are significantly longer than those of females. • Males used their forelegs to hold up a female from below. • Besides forelegs, males have longer tails than females. • Our results represent the first observation of swarm mating behavior in E. orientalis . Swarming and mating behaviors of a mayfly species, Ephemera orientalis Mclachlan, 1875 were observed in 2015, 2016, and 2018 at a river bank of the Asahi River, Japan. Males started to make swarms between late April and middle May in 2016 and 2018. The numbers of mated pairs in a swarm correlated with the numbers of flying males in a swarm in 2016 and 2018. Swarms were formed during a limited period at dusk most probably because that interval is free from natural enemies. Males competed with each other to copulate with females in swarms. We clarified the function of the forelegs of males, which are significantly longer than those of females. Males used their forelegs to hold up a female from below. Besides forelegs, males have longer tails than females. We will discuss why sexual differences are found in these traits. Our results represent the first observation of swarm mating behavior in E. orientalis .
Highlights
Many animal species show species-specific mating systems, and they often form aggregations including leks and swarms to mate (Thornhill and Alcock, 1983)
Ephemera japonica emerges from June to August, and emergence of Ephemera ori entalis, which is the targeted species of the present study, is able to observe even in summer and autumn seasons (Maruyama and Hanada, 2016), but the mating behavior in swarms of Ephemera orientalis have not been investigated
Males who were resting on individual leaves of surrounding trees first flew away from the leaves, and started to form swarms
Summary
Many animal species show species-specific mating systems, and they often form aggregations including leks and swarms to mate (Thornhill and Alcock, 1983). Ephemera japonica emerges from June to August, and emergence of Ephemera ori entalis, which is the targeted species of the present study, is able to observe even in summer and autumn seasons (Maruyama and Hanada, 2016), but the mating behavior in swarms of Ephemera orientalis have not been investigated. In the present study, we observed the swarming and mating behaviors of Ephemera orientalis along the river bank in Okayama, Japan.
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