The mystery of how spiders extract food without masticating prey

Abstract

Standard accounts of how spiders obtain food without masticating their prey are probably largely wrong. Species in the families Uloboridae, Thomisidae, Araneidae and Theridiidae do not inject digestive fluid into the prey’s interior, nor do they suck fluids directly from its interior. Rather they regurgitate fluid onto the surface of the prey, and then suck it back up from there. Philoponella vicina and other uloborids are extreme in this respect: they wet the entire outer surface of the prey package simultaneously with digestive fluid, and their mouthparts often never touch the prey. Capillarity (along with digestion of prey membranes in Philoponella) is apparently responsible both for the dispersion of digestive fluid into the prey, and the exit of liquids from inside the prey.