by Jillian Cowles
After a monsoon thunderstorm, the night becomes alive as millipedes, toads, and tarantulas appear as if by magic. With a leg span of 4 to 5 inches, it is no wonder that the desert blond tarantula, Aphonopelma chalcodes, has become an iconic symbol of the Arizona desert. But perhaps most residents of our fair state would be surprised to learn that Arizona boasts a rich diversity of tarantulas rivaling that of California and Texas. Of the 29 species of tarantulas native to the United States, 17 are found in Arizona. Three of those species can be found in the Vail area: Aphonopelma chalcodes, Aphonopelma vorhiesi (with a 3-inch leg span), and the tiny Aphonopelma saguaro (with 1.5 inch leg span).
The geography of southern Arizona provides the perfect storm for biological diversity. Temperate organisms from the north meet tropical organisms from the south. The Sonoran Desert, with its characteristic saguaros, meets the Chihuahuan Desert starting only a few miles southeast from Vail. And finally, our mountains provide a whole range of elevations for a variety of plant and animal species. Some populations become isolated on these “sky islands” and with time, some of these isolated populations have evolved into new, distinct species. Consequently, Arizona has several newly described species of tarantulas, including Aphonopelma madera from the Santa Rita and Huachuca Mountains, Aphonopelma catalina from the Catalina Mountains, and Aphonopelma superstitionense from the Superstition Mountains.
All of our native tarantulas live in burrows underground, only emerging to hunt or look for mates. The familiar sight of tarantulas wandering during the monsoon season is due to mature males looking for females. Once the male finds the burrow of a female, he drums on the ground, sending her a message in her underground burrow. She answers back by also drumming on the ground. If she is willing to mate, she emerges with her fangs extended, so that the male can hook his tibial spurs under the fangs and lift her upright. After the male mates with her, the female might kill and eat the male if he is not quick enough in his escape.
Some months later, the female produces an egg sac containing several hundred eggs. She carefully tends the eggs, guarding them and moving the sac within the burrow to the most favorable spot for incubation. The babies are ready to leave their mother’s burrow during the summer monsoon season. One night, one by one, the tiny pink, white and black babies exit the burrow, following each other in single file until they form a chain across the desert floor. The chain fragments as the babies disperse to start their own solitary lives. It can take 7 to 10 years for a tarantula to reach maturity. The males die shortly thereafter, but the females can live for decades. And so the monsoon season is the time of the tarantula: a time for the babies to start their new lives, a time for wandering and mating, and a time for death.