Ultrafast launch of slingshot spiders using conical silk webs

Short-range hunters: exploring the function and constraints of water shooting in dwarf gouramis

“…Tool use and similar behavioural adaptations that expand foraging limits are relatively rare but not as taxon exclusive as once thought (Hansell and Ruxton, 2008;Seed and Byrne, 2010;Brown, 2011;Shumaker et al, 2011). Ballistic predation, where an object or body part is used as a projectile to capture prey (Sakes et al, 2016), is similarly rare, but occurs across a wide variety of taxa -such as the salamanders from the genus Hydromantes (Deban and Richardson, 2011), mantis shrimp (Patek et al, 2004), slingshot and spitting spiders (Alexander and Bhamla, 2020;Suter and Stratton, 2013), Loligo squid species (Kier and Leeuwen, 1997), and humans (Wood et al, 2007;Roach et al, 2013). Ballistic predation can be used to expand the foraging limits and among non-human animals one of the more notable examples is the archerfish (Toxotoes spp) with an impressive shooting ability that allows them to prey on terrestrial and aerial targets in addition to their aquatic prey (Elshoud and Koomen, 1985;Salini et al, 1990;Schuster, 2007).…”

Slingshot spiders build tensed underdamped webs for ultrafast launches and speedy halts

“…The sit and wait strategy of many orb-weaving spiders is well known for the ability to effectively snare prey using sticky silk and the rapid dissipation of the captured prey's kinetic energy (Das et al, 2017;Kelly et al, 2011;Sensenig et al, 2012;Yu et al, 2015). Slingshot spiders, orb-weavers known for extending and releasing their webs like slingshots to capture prey, evolved an orb web modified with a tension line attached at its central hub (Alexander and Bhamla, 2020;Alves et al, 2007;Coddington, 1986Coddington, , 2005Eberhard, 1981Eberhard, , 1986Eberhard, , 1990Hingston, 1932;Wienskoski, 2010). The tension line enables the spider to deform its web into a 3-D conical structure, loading elastic energy into the radial lines that ultimately facilitates rapid accelerations (> 1300 m/s 2 ) for capturing flying prey (SI Movie 1), or possibly avoiding predation (Alves et al, 2007).…”

“…The tension line enables the spider to deform its web into a 3-D conical structure, loading elastic energy into the radial lines that ultimately facilitates rapid accelerations (> 1300 m/s 2 ) for capturing flying prey (SI Movie 1), or possibly avoiding predation (Alves et al, 2007). Although in previous work, we described how the slingshot spider loads the web as a spring to achieve ultrafast motion (Alexander and Bhamla, 2020), it remains unclear how the spider leverages its unique web and tension line to decelerate quickly and come to a halt, either after successful capture or missing of prey (Eberhard, 1990), and to reset its web to potentially fire again. What are the relevant physical forces governing energy storage and energy dissipation in the web?…”

“…The slingshot spider grips the center of its web with four rear legs while incrementally pulling and twisting the tension line and coiling the silk with claws on its anterior legs and pedipalps (non-locomotor anterior appendages) to store elastic energy in the radial lines of the web (Fig. 1a) (Alexander and Bhamla, 2020;Coddington, 1986). Upon sensing external stimuli (for example a finger snap), the spider releases the tension line, catapulting both the web and spider backwards (Fig.…”

“…The dominant movement is mostly in the y-direction (10 -15 mm or 10-15 × body lengths) with smaller movements (±1.1 mm, less than one body length) in the x-direction. Spiders achieve vertical speed of up to 4.2 m/s (v max = 4.16 ± 0.07 m/s) and accelerations exceeding 1300 m/s 2 (a max = 1163 ± 144 m/s 2 ) (Alexander and Bhamla, 2020). Despite this ultrafast millisecond motion, we observe that the resultant vibrational response of the web attenuates within milliseconds as well -suggesting that the web design facilitates both energy storage and speed as well as energy dissipation, which could potentially improve prey capture, reduce the probability of damage to spider or web, and/or facilitate rapid reset and reloading of the web.…”