A spider's vibration receptor: its anatomy and physiology.

The common house spider, Achaearanea tepidariorum , has a sensitive vibration receptor on each of its eight legs. This receptor is the tarso-metatarsal lyriform organ, and while it may not be the only vibration receptor the spider has, it appears to be the most sensitive. The 10 receptor units of which the sense organ is composed are all sharply tuned to specific frequencies between 60 and 1400 cps, but the sensitivity of each receptor unit depends upon the tension of the slits of the lyriform organ. Physiological experiments have shown that the tuning of the receptors occurs only in response to air-borne sound; no discrimination is made of frequencies of web-borne vibration. One can speculate that the high sensitivity to air-borne sound is a consequence of the relatively poor transmission of vibration through Achaearanea's web.