Abstract
We traced the evolution of silk use by spiders in attacks on prey by combining previous publications with new observations of 31 species in 16 families. Two new prey‐wrapping techniques are described. One, in which the spider holds a tense line (often covered with viscid silk) with both legs IV and applies it to the prey with a simultaneous movement of both legs, may be a synapomorphy linking Theridiidae, Nesticidae, and Synotaxidae. The other, in which the spider stands over the prey and turns in place, is apparently very ancient; it occurs in Theraphosidae, Tengellidae, and Agelenidae. The use of legs IV to wrap prey is described for the first time in Filistatidae and Scytodidae. Using a recent phylogeny of spiders, we propose that prey wrapping with legs IV has evolved convergently at least four times. We propose that prey wrapping originally evolved from egg‐sac construction behaviour.
Highlights
The production of silk lines that emerge from abdominal spinnerets is a defining feature of spiders (Shear et al 1989), and many spiders use such silk lines to wrap prey (Foelix 1996)
The silk that spiders use to wrap prey is presumed to come from aciniform silk glands, there is little direct evidence (Weng et al forthcoming); and pholcids wrap prey despite lacking acciniform glands, while ampullate gland silk is probably used in Nephila clavipes
Silk was pulled from the posterior lateral (PL) spinnerets by dabbing the spinnerets and the abdomen to make an attachment to the substrate and pulling away, rather than by pulling lines from the spinnerets with legs IV as in the other species we observed
Summary
The production of silk lines that emerge from abdominal spinnerets is a defining feature of spiders (Shear et al 1989), and many spiders use such silk lines to wrap prey (Foelix 1996). There are at least two contexts in which spiders wrap their prey: to restrain active prey so they cannot escape (‘‘immobilization wrapping’’); and to form more compact, manageable packages of already immobilized prey to facilitate other activities such as removing it from the web, carrying it, fastening it to the web at the feeding site, or feeding (‘‘postimmobilization wrapping’’) (Eberhard 1967; Robinson et al 1969; Robinson and Mirick 1971; Rovner and Knost 1974; Robinson 1975; Nitzsche 1988). We present some behavioural details as ‘‘new’’, but most previous studies cannot be checked for the occurrence of some subtle details, such as the positions of different spinnerets, or the alternate versus simultaneous use of legs IV to apply wrapping silk to the prey Some of these ‘‘new’’ details may well occur in other species that have been studied previously
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