Studies on the ecology of orb spiders have focused on diurnal spiders, especially field studies. Nocturnal spiders, however, face different conditions due to the type of prey found at night. A field study was conducted to observe the activity of adult females of Eriophora edax in their natural environment, and to analyze their predation efficiency and web retention properties. Most of the spiders were observed around sunset, which suggests that E. edax tends to build webs in the early evening. In order to evaluate the predation efficiency of E. edax we compared its behavior and web retention properties with the behavior of a diurnal orb-weaving spider, Verrucosa arenata. Two prey types, a diurnal Hymenoptera and a nocturnal Lepidoptera, were selected and presented to the spiders, to record approach time and prey capture time. The results showed that E. edax spent more time to capture Hymenoptera than to capture Lepidoptera. During the experiments of web prey retention time, Hymenoptera consistently showed greater tumbling than Lepidoptera, but the total retention time was the same for both prey types. Our results showed that E. edax forages strictly at night and, in terms of prey capture and web retention, was more efficient when preying on Lepidoptera.