The Desert Tarantula, Aphonpelma chalcodes, is the most common tarantula seen in the Tucson area and is one of 30 species found in Arizona. Now, during the monsoon, and into early fall is the time to see them. If you notice holes in your yard about the size of a quarter, it is probably a tarantula hole. You can go out at night with a flashlight and observe the females near their holes. Males are more likely to be seen trekking to find females.
Tarantulas are primitive spiders that evolved almost 350 million years ago and have changed little since. The female Desert Tarantula is usually tan or brownish, while the male is darker, usually with black or dark legs and a reddish abdomen. Females have a large abdomen, bigger than the cephalothorax(upper body), while the males have a small abdomen.
Tarantulas dig burrows about 6 inches deep and up to 8 inches laterally, enlarging them as the spider grows. The spiders molt 3- to 6 times a year as they grow, and they can regenerate lost legs upon molting.
Tarantulas are venomous like all spiders, but they are very docile and bite only under extreme provocation. I have picked up many tarantulas and never have been bitten. The venom is usually not harmful to humans. But tarantulas have another defense. Some of the hairs on their abdomen are barbed (urticating hairs) and are very irritating. The tarantula uses its hind legs to flick these hairs at an attacker.
Tarantulas are long lived spiders. They reach sexual maturity at 8- to 12-years old. Females can live up to 25 years, but the males live only one season beyond sexual maturity. Mating takes place in the summer and fall, and the female stores the sperm until the next spring. The female spins a thick layer of silk in her burrow and in concealed places near the burrow to hold up to 300 eggs. Ants are the main predators of the eggs. The spiderlings hatch in about three weeks and stay in the silk cocoon for another 7 weeks while they grow. The survivors disperse and make their own burrows.
When active, tarantulas may set out strands of silk, “trip wires” around their burrow as a signal that a meal is passing by. They don’t like water, and flee if the burrow gets wet. Sometimes a silk cap on the burrow helps keep water out. Tarantulas do need to drink, but can go up to 90 days without water. During the winter, tarantulas become dormant. They plug their holes with silk and soil, and wait for summer.
And now for a gruesome tale. The Pepsis wasp, Pepsis formosa, is a large (up to 2 inches), bluish-black wasp with orange wings. It is also know as the tarantula hawk. It is a parasite on tarantulas and uses the spiders in its reproductive cycle.
The Pepsis wasp will approach a tarantula and cause the spider to rear its legs, thus exposing its abdomen. The wasp will sting the spider to paralyze it. The wasp will lay an egg on the paralyzed spider and drag it to a hole, bury it, and cover up the hole. When the wasp egg hatches, the larvae eats the flesh of the living tarantula for about 35 days, then spins a cocoon and pupates over the winter. If the wasp egg fails to hatch, the spider can recover. These large wasps generally don’t bother humans.
Tarantulas may look scary, but they are very gentle creatures. You need not be aftraid.