Trophic niche and capture efficacy of an ant-eating spider, Euryopis episinoides (Araneae: Theridiidae)

Abstract

In this study, field and laboratory observations of the feeding ecology (natural diet, prey acceptance, prey capture behavior and capture efficacy) of the theridiid Euryopis episinoides Walckenaer, 1847 were combined to reveal its trophic niche and capture efficacy and to test the hypothesis that this species is an ant-eating specialist. Natural prey was investigated from individuals collected in southern Portugal and was found to contain only ants of several species. Prey acceptance experiments revealed that spiders accepted several prey types occasionally, but ants, termites, and fruit flies were accepted with a high frequency. Prey capture behavior was similar for four tested prey types (Formicinae and Myrmicinae ants, termites, and fruit flies). Hunting usually started with a wrapping sequence when the spider threw the silk from its spinnerets onto the prey while circling around it. Then the spider bit the prey and wrapped it in more silk. Afterwards the spider waited for some time until the venom paralyzed the prey. Finally, the spider attached the immobilized prey to its spinnerets and carried it away before feeding. Wrapping time, number of bites, and waiting time differed among the four prey types, with the longest wrapping time, the highest number of bites, and the longest waiting time recorded during the capture of Myrmicinae ants. We conclude that E. episinoides is an ant-eating specialist possessing an effective capture strategy for the capture of ants. Yet, E. episinoides spiders maintain the ability to capture alternative prey.