Vibrations in the orb web of the spider Nephila clavipes: cues for discrimination and orientation
- Cite this article as:
- Landolfa, M.A. & Barth, F.G. J Comp Physiol A (1996) 179: 493. doi:10.1007/BF00192316
- 410 Downloads
Transmission of natural and artificial 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 50 dB. 2. Transmission of longitudinal vibrations along individual radii was attenuated over ca. 12 cm 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 70–1500 m/s resulted in time-of-arrival differences at the spiders tarsi of < 1.5 ms, which may be too brief for stimulus direction determination.
Key wordsSpider web Nephila clavipes Vibrations Discrimination Localization
laser Doppler vibrometer/-metry
radius of gyration