Food availability influences adult body mass variability and reproductive traits in a spider.

All animals require food to survive, grow, reproduce, and thus optimize fitness in nature. Food availability can profoundly affect demographic parameters such as longevity and fecundity. Here, we compared reproductive parameters in the false widow spider, Steatoda grossa (Araneae, Theridiidae), when the availability and size of prey (the house cricket, Acheta domesticus) were manipulated. Adult mated female spiders that were fed weekly (constant prey treatment) produced more progeny during their lifetime than females fed every 3 weeks (intermittent prey treatment). Furthermore, the monitoring of fecundity schedules showed that over the first 10 egg sacs, the mean number of neonate spiderlings per egg sac was around 40% higher in constantly fed than intermittently fed spiders. Time intervals between egg sac productions were generally higher when prey availability was lower. Some females lost more than 50% of their body mass after the production of the first egg sac, although reproductive investment tended to decrease thereafter. The amount of prey offered to females significantly affected mass gain between reproductive events, but fewer progeny were produced by females per egg sac, as well as cumulatively over the first three egg sacs, when they were only fed small prey. Starved females that had not produced egg sacs in several months exhibited total reproductive recovery when fed. Our results demonstrate the importance of prey attributes on S. grossa reproduction. Furthermore, females invest remarkably large amounts of resources during each reproductive cycle and over the course of a lifetime.