Larger females do not achieve higher lifetime fecundity in an extremely size-dimorphic spider

Female body size is often linked positively to clutch fecundity because size limits the number of eggs or offspring produced per clutch. Yet larger clutches may not increase lifetime reproductive success if offset by fewer reproductive events, shorter lifespan, reduced offspring survival, or mating-rate constraints. We tested this in the African hermit spider, Nephilingis cruentata , an extremely size-dimorphic species in which mating plugs restrict females to one or two lifetime copulations. Larger females produced heavier clutches, i.e., egg-sacs, indicating greater per-clutch fecundity, but produced fewer egg-sacs and had longer inter-egg-sac intervals. Consequently, total egg-sac mass, used as a lifetime fecundity proxy, did not increase with female size. In a standardised offspring sample, larger maternal size did not increase the probability that hatchlings reached sexual maturity. Females often produced several viable egg-sacs followed by a terminal phase of non-viable egg-sacs; viability declined with time since mating. This continued oviposition after viable reproduction shows that females retained the capacity to produce egg-sacs and is consistent with fertilisation limitation. However, the data do not distinguish fertilisation failure from sperm deterioration, oocyte or reproductive-tract ageing or embryo failure. Thus, in the African hermit spider with a strongly restricted mating system and reared under laboratory conditions, female body size predicts per-clutch but not lifetime fecundity.