Thermal Preferences of Cowpea Seed Beetles (Callosobruchus maculatus): Effects of Sex and Nuptial Gift Transfers

Abstract

The thermal environment influences insect performance, but the factors affecting insect thermal preferences are rarely studied. We studied Callosobruchus maculatus seed beetles and hypothesized that thermal preferences are influenced by water balance, with individuals with limited water reserves preferring cooler habitats to reduce evaporative water loss. Adult C. maculatus, in their flightless morph, do not consume food or water, but a copulating male provides a female with a nuptial gift of ejaculate containing nutrients and water. We hypothesized that gift recipients would prefer warmer habitats than gift donors and that both sexes would plastically adjust their thermal preferences according to the size of the transferred gift. We measured the thermal preference in each sex in individuals that were mated once or were unmated. In the mated group, we measured the sizes of the nuptial gifts and calculated proportional body mass changes in each mate during copulation. Supporting the role of water balance in thermal preference, females preferred warmer habitats than males. Nevertheless, thermal preferences in either sex were not affected by mating status or gift size. It is likely that high rates of mating and gift transfers in C. maculatus living under natural conditions promoted the evolution of constitutive sex-dependent thermal preferences.

Male Mediterranean fruit flies prefer warmer temperatures that improve sexual performance

“…In Glossina brevipalpis, flies exhibit postprandial thermophily where warmer temperatures are preferred after a blood meal to improve digestion (both sexes blood-feed) (McCue et al, 2016). Females of Callosobruchus maculatus prefer warmer temperatures than males but the reason for this is unknown (Malek and Czarnoleski, 2021). In male Locusta migratoria and both sexes of Tenebrio molitor, individuals thermoregulate behaviourally to optimise assimilation of dietary intake (Coggan et al, 2011;Rho and Lee, 2017).…”