Abstract

Background. In animals, females often outlive males, though the opposite also occurs. It remains unclear whether sex-biased longevity is tied to being male or to sex chromosome heterogamety. To address this question, lepidopteran insects are a good model because females are heterogametic (ZW), while males are homogametic (ZZ).

Methods. We conducted a meta-analysis of lifespan data from the literature to assess sex-biased longevity in Lepidoptera. Sources included Google Scholar, Web of Science, Research Rabbit, and the AnAge database (2020–2024). Papers were included if they reported adult longevity with explicit values and clear methodologies. We used R to calculate log₂ longevity ratios between sexes for each species, testing deviations from equality with t-tests and binomial tests. For species with temperature data, we performed linear regression on ratios. Phylogenetic structure was assessed with Abouheif’s C_mean using a species tree recreated from published phylogeny.

Results. Of 47 references identified, 40 were included for analysis. Four used wild populations for their observations while 36 used populations reared in laboratory conditions. We analyzed longevity data for 38 species in 13 families. 22 species had male-biased longevity and 16 species had female-biased longevity. There was also no clear phylogenetic relationship in the sex-biased longevity patterns. However, for a few species with data available at different temperatures, we did observe a qualitative pattern of increasing female-biased longevity at warmer temperatures.

Discussion. This suggests that heterogamety versus homogamety is unlikely to broadly influence sex-biased longevity among Lepidoptera, though it could still be a factor in individual species. Our temperature results indicate the environment may play a significant role in sex-biased longevity in Lepidoptera. Some of our sources included data on other environmental factors, such as pest control, host plant, and photoperiod, which can also affect longevity, but as the results from each source were not directly comparable, we did not explore if these variables influence broad patterns of sex-biased longevity. Some of our sources reported maximum longevity values as well, which can show different patterns than average longevity, but for the purposes of this meta-analysis we treated these values in the same manner. Future research should investigate the effects of temperature and other environmental variables on sex biased longevity more broadly, as well as possible effects of variable or missing W chromosomes.

Funding. This work was provided by US National Science Foundation grant DBI-2213824, as well as the George Gould and University of Kansas Undergraduate Research Awards.