Body spot coloration of a nocturnal sit-and-wait predator visually lures prey

Many nocturnal spiders have paired conspicuous yellow ventral spots that contrast against their black and brown abdomens. A previous experiment, manipulating the coloration of the spots of the spider Neoscona punctigera, suggested that the spots lure prey. We conducted a field experiment in which we placed spider dummies that either mimicked an adult female N. punctigera in coloration, size, and shape (standard dummies) or mimicked N. punctigera but with the coloration of their ventral spots manipulated onto orb webs in the field at night and monitored them with infrared video cameras. Spectrophotometry confirmed that the coloration of the dummies resembled spider bodies, with the exception of the spots of the gray spotted dummies, where chromatic and achromatic contrast differences from spider spots were found. We used entirely yellow dummies to assess whether the spots represent a compromise between prey attraction and predator avoidance. We found that the standard dummies, mimicking adult female N. punctigera in coloration, size, and shape, attracted more prey than the dummies with gray spots, the entirely black dummies, and webs without spiders. The entirely yellow dummies attracted fewer prey than the standard dummies. These results show that the coloration of nocturnal spider ventral spots lures prey, although whether chromatic or achromatic cues are used could not be identified. The entirely yellow dummies did not lure more prey than standard dummies, so the spots are unlikely to represent a compromise between prey attraction and predator avoidance, in contrast to the coloration of certain diurnal orb web spiders.