Nursery Web Spider

Pisaurina mira — the nursery web spider — is one of about 350 species in family Pisauridae (the nursery web spiders) and one of the most-cited examples of NUPTIAL GIFT-GIVING in arachnid biology. The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Mexico. Adults are 12-17 mm body length, with a tan-brown body marked by a darker longitudinal band running down the dorsal abdomen. Pisaurina mira is the most common nursery web spider in eastern NA. The species' major behavior is NUPTIAL GIFT-GIVING. Males offer FOOD GIFTS to females during courtship — the male captures a prey item (typically a fly or other small insect), wraps it in silk, and presents it to the female before mating. The female accepts the wrapped prey gift and consumes it during the act of mating, while the male copulates with her. The nuptial gift serves multiple functions: (1) PROVISIONING — the female receives a substantial nutritional benefit during mating, important for her egg-laying and reproductive success; (2) DISTRACTION — the female is occupied with eating the gift and less likely to predate the male during mating (a real risk in many spider species — sexual cannibalism is common in arachnid mating); (3) MATING ACCESS — males that bring larger or more nutritious gifts are more likely to be accepted as mates, providing a selection mechanism for male foraging quality. Some male nursery web spiders have evolved a 'CHEATER' strategy — wrapping in silk an inedible object (a leaf, a piece of debris) that LOOKS like a wrapped prey gift but contains no food. The deceptive males extend mating duration during which the female unwraps the empty package, but females that detect cheating attack and predate the male. The male nuptial-gift-giving and male-cheating behaviors are featured in essentially every modern textbook discussion of arachnid sexual selection. The species also gives the family its name through the FEMALE'S DRAMATIC MATERNAL CARE: females construct large 'NURSERY WEBS' of silk in vegetation (typically 5-10 cm diameter, supported by leaves or twigs) that contain the egg sac during embryonic development. The female guards the nursery web and the contained spiderlings (typically 100-200 spiderlings per egg sac) until they have molted once and dispersed (1-2 weeks). The species is harmless to humans and a major beneficial garden predator.