Bathyplectes anurus, a parasitoid of the alfalfa weevils, forms a cocoon in the late larval stage and exhibits jumping behaviour. Adaptive significance and costs of the cocoon jumping have not been thoroughly studied. We hypothesised that jumping has the fitness benefits of enabling habitat selection by avoiding unfavourable environments. We conducted laboratory experiments, which demonstrated that jumping frequencies increased in the presence of light, with greater magnitudes of temperature increase and at lower relative humidity. In addition, when B. anurus individuals were allowed to freely jump in an arena with a light gradient, more cocoons were found in the shady area, suggesting microhabitat selection. In a field experiment, mortality of cocoons placed in the sun was significantly higher than for cocoons placed in the shade. B. anurus cocoons respond to environmental stress by jumping, resulting in habitat selection. In the presence of potential predators (ants), jumping frequencies were higher than in the control (no ant) arenas, though jumping frequencies decreased after direct contact with the predators. Body mass of B. anurus cocoons induced to jump significantly decreased over time than cocoons that did not jump, suggesting a cost to jumping. We discuss the benefits and costs of jumping behaviour and potential evolutionary advantages of this peculiar trait, which is present in a limited number of species.

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Site fidelity and long-distance homing are known to occur in nesting female Hymenoptera. We report here on the site fidelity and homing ability in males of five species of scoliid wasps (Hymenoptera: Scoliidae), a group whose females do not make nests but are ectoparasitoids of scarabaeid beetles (Coleoptera: Scarabaeoidea). The males of these wasp species patrol female emergence areas searching for mates. Based on mark-recapture data, we found that between 40% and 100% of marked males left the release area and travelled 50–800 m from the point of capture returning to their original patrol area. We discuss the adaptive significance of site fidelity and homing behaviour in Scoliidae, and propose hypotheses about the evolution of the homing behaviour in Hymenoptera. The homing ability of these primitive Aculeata may represent a case of convergent evolution with other Hymenoptera in which males patrol emergence areas in search of females. Additionally, this homing ability may serve as a preadaptation for the evolution of nest-provisioning and nesting habits in Hymenoptera.

Hypera postica is a univoltine invasive pest of alfalfa, Medicago sativa, in North America. In Japan, H. postica was first found in 1982 from Fukuoka and Okinawa Prefectures and became a serious pest of Chinese milk vetch, Astragalus sinicus, cultivated as a honey source for humans and green manure for rice. In North America, three strains, Western, Eastern and Egyptian, have been identified and the Western strain is infected with Wolbachia, which causes complete inter‐strain reproductive incompatibility. In contrast, only Western and Egyptian strains had been reported throughout Japan and none of the Western strain examined for the Fukuoka populations in northern Kyushu was infected with Wolbachia. First, we screened populations from northern Kyushu collected since 1982 for geographical and chronological distribution of the Eastern strain. The Eastern strain has been found at low frequencies since 1985 and is still present in 2014. Second, we experimentally tested our hypothesis that inter‐strain crosses between uninfected Western‐strain males and Egyptian‐strain females should produce viable offspring. We crossbred virgin adults reared individually from field‐collected larvae and confirmed that the F1 eggs of crosses between the Western‐strain males and the Egyptian‐strain females develop successfully into larvae.