Vibrations in the orb web of the spider Nephila clavipes: cues for discrimination and orientation

Abstract

Transmission of natural and arteficial vibrations in webs of Nephila clavipes was examined using laser Doppler vibrometry to determine how this spider discriminates and localizes stimuli. 1. Vibration signals of four entrapped insect species peaked at different frequencies from 5--30 Hz, but their spectra overlapped considerably. Peak amplitudes spanned 50dB. 2. Transmission of longitudinal vibrations along individual radii was attenuated over ca. 12cm by 4.0 + 2.7 dB; attenuation values for transverse and lateral vibrations were 22.2 _+ 4.6 dB and 26.2 _+ 4.3 dB, respectively. Some transmission spectra characteristics may be explained by "resonances" of the spider and threads. 3. Radial thread transmission increased by 2.2-5.8 dB after cutting the connecting auxiliary spirals, demonstrating that vibrations "leak" from stimulated radii via these threads. Auxiliary spirals provide structural support to Nephila webs at the expense of degraded directional transmission. 4. Upon single-point stimulation, vibrations measured around the web hub and at the spider's tarsi revealed 2-D vibration amplitude "gradients" of 20-30 dB indicating the stimulus direction. In contrast, measured vibration propagation velocities of 70-1500m/s resulted in time-of-arrival differences at the spiders tarsi of < 1.5 ms, which may be too brief for stimulus direction determination.

Dangerous mating systems: Signal complexity, signal content and neural capacity in spiders

“…With the advent of non-contact methods of recording vibrations, such as laser vibrometry, the field has made substantial advances in recent years (e.g. Landolfa and Barth, 1996;Elias et al, 2006;Hebets et al, 2008;Wignall and Herberstein, 2013a).…”

The hub as a launching platform: rapid movements of the spider Leucauge mariana (Araneae: Tetragnathidae) as it turns to attack prey

“…3, 4, 0:012). Probably the spider determined the direction of the prey by comparing the intensities of longitudinal vibrations of different lines (Landolfa & Barth 1996), and presumably the locations of prey that struck the web behind the spider were sensed mainly by her legs III and IV, on or near the radii closest to the prey. The probable importance of radii in transmitting vibrations is supported by the nearly threefold increase in the delay before the spider began to turn when all but five radii were cut (a mean of 0.18 s as opposed to 0.055 s, P , 0.001 with Mann-Whitney U Test), perhaps due to reduced amplitude of the vibrations or a greater difficulty in localizing their source.…”

Attention focusing in a sit-and-wait forager: a spider controls its prey-detection ability in different web sectors by adjusting thread tension

“…In the laboratory, the spiders were observed to pull on vertical radii more strongly than on horizontal radii. Orb-web spiders depend on mechanical senses to perceive events around them (Barth 2002), and events such as prey interception produce vibrations that are transmitted through the web threads and sensed by the spider (Masters & Markl 1981;Landolfa & Barth 1996). When the spider pulls on radii, the thread tension is likely to increase.…”