The range of trophic niches in spiders varies from very wide, including prey of several insect orders, other arthropods, and even nectar and other plant products, to very narrow, restricted to specific prey types, such as ants. Previous studies showed that the effects of a mixed diet are beneficial to fecundity, survivorship, and growth rate for some species but not others. This study evaluated the impact of a varied diet and monotypic diets of beetles, ants, and termites for Tidarren haemorrhoidale (Bertkau, 1880) a cobweb spider. Adult females were collected in a Eucalyptus plantation, kept in captivity, and divided into four experimental groups; each submitted to one of these diets for 125 days. Beetles were valuable prey for proteins and lipids compared to the alternatives. Termites and ants had equivalent contents of proteins, but termites were richer in lipids. Two monotypic diets composed of the main prey types (beetles and ants) had similar effects on fecundity and body mass compared to the mixed diet. Although termites have more lipids than ants and have a higher proportion of their biomass consumed, the monotypic diet of termites caused weight loss for spiders over time and reduced fecundity. Survivorship in all groups was similar. These results indicate that a diversified diet is not required for T. haemorrhoidale to achieve its maximum reproductive potential. This characteristic may be important to ensure the success of this species in colonizing and establishing large populations, even in disturbed habitats with low prey diversity.