Sex-related variation in δ 15 N values of ground beetles (Coleoptera, Carabidae): A case study

•We measured δ13C and δ15N values in male and female carabids from Poland and Russia.•Despite a large variation, males were on average enriched in 15N relative to females.•The enrichment was most pronounced in predatory species during breading season.•Results indicate sex-specific patterns of foraging and/or resource allocation.