Sex Differences in Adult Lifespan in Insects: A Comparative Analysis of the Roles of Phylogeny, Size Dimorphism, and Sex-Specific Selection

Lifespan is a fundamental life-history trait that varies widely among and within species, including between sexes. While comparative studies have greatly advanced our understanding of sex differences in lifespan in vertebrates, lifespan research in invertebrates remains largely limited to a few model species. Here, we present the first broad-scale comparative analysis of sex differences in adult lifespan (SDL) in insects, using literature-derived data on 350 species spanning ten orders. Female adults outlived males in 62% of species, but patterns of SDL varied markedly, even within genera. Across species, SDL showed a weak positive association with sexual size dimorphism (SSD), indicating a general tendency for the larger sex to live longer. The weak phylogenetic signal in SDL and limited explanatory power of SSD suggest that SDL is evolutionarily labile and largely decoupled from body size-related physiological constraints. Instead, variation in SDL likely reflects sex-specific life-history optimization driven by differing reproductive roles.