Tarantulas attack with their… back hair?

ABC news has a story about a tarantula hair attack. You would think that the venom laden fangs were enough to worry about, but it turns out that some species can also launch a mist of microscopic, barbed urticating hairs into your eyes, skin, and lungs; causing intense irritation.

A British man discovered this defensive behavior the hard way. While cleaning the cage of his Chilean Rose tarantula, Grammostola rosea, the man was hit in the face by a fine mist of hairs from the arachnid. He though nothing of it at first, but over a week the barbed hairs in his eye worked their way into his cornea, iris, and even to the retina at the back of the eye. This resulted in extreme irritation that baffled doctors until they spotted the microscopic hairs and the pet-owner remembered the hair misting incident.

This defensive behavior is common in New World tarantulas and some caterpillars. In tarantulas, the urticating hairs are located on the dorsal abdomen, or the palps in the case of the genus Ephebopus. When threatened, they brush the urticating hairs off or their body with rapid leg-flicking motions. Here is a quick video of the behavior (loud soundtrack warning).

Brachypelma smithi tarantula with a bare patch on its abdomen where it has scraped off its urticating hairs during a defense response (left frame). Scanning electron micrograph (SEM) of a Ephebopus palpal urticating hair region after brushing off most of the hairs in a defense response (right frame). A couple barbed urticating hairs are still in their sockets (Foelix et al., 2009).

References:

• Foelix et al., 2009. Palpal urticating hairs in the tarantula Ephebopus: fine structure and mechanism of release. Journal of Arachnology, 37(3):292-298.