October, 2010

Tarantula

Many people find spiders creepy. This is especially true if they are hairy and relatively big. Our largest spider, the tarantula (Aphonopelma sp.) certainly fits that description! Although the individuals we see around our neighborhood are only about 1.5 to 2 inches long, they look much more imposing because of their long legs.

The spider pictured here is a female. It appears that she has ten legs instead of the usual eight. The front pair, which are rather short, are not actually legs but appendages called pedipalps. On males, these are used for mating, but females use them for manipulating food or even for walking. The two short structures at the front of her head are her chelicera which have fangs attached to the undersides.

Female tarantulas may live over twenty years in captivity. They spend most of their time in burrows, but we sometimes see females walking down the sidewalk near our house. Males are more often found, since they must wander in search of females. Their lifespans are much shorter.

The bite of tarantulas is not considered to be dangerous, but it is probably not a good idea to harass any large spider, as they do have fangs and venom. Besides biting, tarantulas have another defense when threatened: they will use their legs to rub hairs off of their abdomen. These are called urticating hairs and are fine enough to float in the air; they irritate sensitive skin, noses, and eyes of mammals (including humans) that might be attacking them, causing itching, pain, and/or a rash.