Life Span Changes of Coffee White Stem Borers, Xylotrechus quadripes (Coleoptera: Cerambycidae) in Response to Directed Homosexual and Heterosexual Interactions

Abstract

Our study on coffee white stem borers, Xylotrechus quadripes investigated the influence of different sex-based clustering factors on beetle survivorship and life spans. Our experiments involved various groups, including individually isolated virgin males, individually isolated virgin females, groups of only males, groups of only females, and mixed-sex groups. First, survivorship reached 100% within the initial 15 days for all groups except for isolated virgin males. In contrast, the survivorship rates of both groups involving only virgin females and only virgin males ranged from 80% to 90% compared to the maximum survival duration.  Notably, in scenarios with males in groups or mixed-gender groups, survival dropped to zero percent after 45 days. Our study also highlighted the comparable costs incurred by males engaging in both homosexual and heterosexual interactions. Males interacting with females and other males exhibited similar survival curves, displaying shorter median life spans compared to isolated virgin males, suggesting that both courting and mounting behaviors, regardless of the recipient's sex, might affect the life span of males. Furthermore, our research revealed that female-female interactions, while less costly than male-male interactions, still reduced survival periods in only the female group. These findings highlight the cost possibly associated with same-sex interactions and shed light on the dynamics of mating behaviors in this beetle. In conclusion, our findings underscore the significance of studying behavioral and life history traits in different environmental contexts. Social circumstances and ecological factors significantly influence sexual differences in lifespan and highlight the complexity of the interplay between reproductive strategies and survival rates in Xylotrechus quadripes.