Hunting Without a Web: How Lycosoid Spiders Subdue their Prey

Abstract

More than half of all spider species hunt prey without a web. To successfully subdue their prey, they use adapted capture behaviour and efficient grasping mechanisms to interrupt the prey's locomotion, and to restrain it from escaping during the subsequent handling for final envenomation. In this study, we investigated how the prey capture behaviour of different lycosoid spider species is related to leg morphology and venom efficiency; using high speed videography, feeding experiments, stereomicroscopy, scanning electron microscopy and LD 50 venom bioassays. We found that different species employed different techniques when grasping their prey and these differences strongly correlate with the distribution and size of hairy adhesive leg pads (so-called scopulae on pro-and retrolateral parts of legs) and erectable spines, which act in a complementary way. Our results indicate that the grasping and handling behaviour and leg morphology is crucial in restricting the prey's movements. However, none of these traits is directly related with venom efficiency.

Morphology and evolution of scopula, pseudoscopula and claw tufts in Mygalomorphae (Araneae)

“…This hypothetical mechanism is congruent with the observations of Pérez-Miles et al (2015) but differs from results by Niederegger and Gorb (2006) who found higher adhesion on scopula when the leg pushes in the theraphosid Aphonopelma seemanni. Rovner (1978), Foelix et al (1984), Pekar et al (2011), and Eggs et al (2015) proposed the participation of scopulae in prey manipulation in Araneomorphae but some characteristics we found in Mygalomorphae at first question this function. This is only applicable to apical scopula or claw tufts considering that the adhesive faces of most part of scopula setae are oriented dorsally (distally) facilitating pushing adhesion.…”

“…Other interpretation is related with the full control of prey by predator due to the mechanics of moveable setae. Eggs et al (2015) proposed that erectile scopular setae Fig. 12 Actinopodidae and Idiopidae.…”

“…However, fine structure and function of adhesive setae in mygalomorphs are severely understudied. Several authors stressed on the importance of adhesive setae in two functions: prey capture and locomotion (Homann 1957;Rovner 1978Rovner , 1980Dunlop 1994;Foelix 2011;Pekar et al 2011;Foelix et al 2012;Niederegger 2013;Gorb 2012a, 2015;Lapinski et al 2015;Eggs et al 2015).…”

Hunting with sticky tape: functional shift in silk glands of araneophagous ground spiders (Gnaphosidae)

“…We presume that the spiders start swathing after an assessment of the prey's strength and dangerousness, because it was never started without previous physical contact with the prey. For direct attacks, the dense hairy adhesive pads (scopulae) in the front legs help the spider to hold onto the prey's body and subdue it (Eggs et al, 2015;Grimm, 1985;Wolff and Gorb, 2012;Wolff et al, 2013) (Fig. 1R).…”

Biomimetic Spider Leg Joints: A Review from Biomechanical Research to Compliant Robotic Actuators

“…The characteristics of spider legs are multi-fold: On the one hand, they are highly sensitive, move gracefully and have a lightweight design, which is apparent, since some spiders are able to walk on the surface of water [15]. On the other hand, for hunting and climbing tasks, an impressive dynamic and powerful actuation can be observed [16,17]. Thus, the spider leg system combines flexible and lightweight movements with powerful actuation; it is a biological showpiece for biomimetic applications and perfectly corresponds to major requirements for modern robotic applications.…”