Tarantula foot hair. Coloured scanning electron micrograph SEM of hair from a Mexican red_kneed tarantula Brachypelma smithi. Tarantulas are poisonous spiders that hunt insect prey. This tarantula does not have very good vision, mostly relying on its sensitivity to noise and vibrations, detected with its leg hairs. Noise and vibrations move the hairs in their sheaths, thus alerting the spider. The hairs on the legs of this tarantula are also shed as a defence, and cause intense itching. B. smithi has a body length of around 10 centimetres. It is nocturnal, and it is found in the deserts of Mexico and the southern USA.