August 15, 2025, 3:14 pm | Read time: 6 minutes
While some people refuse to accept that summer is ending, others eagerly anticipate the arrival of fall, cooler temperatures, and the spooky atmosphere of darker days. In some U.S. states, however, it’s not Halloween horror movies that set the mood, but thousands of Texas tarantulas and other bird spiders that become more visible starting in late August each year.
Tarantulas Use Fall for Mating
Are you among those who, by the end of August, bring out the orange decorations from the basement and consume practically nothing but “Pumpkin Spice” products? On social media, fall has long arrived—and in the U.S., it includes the big crawl: Particularly noticeable is the behavior of the Brown Texas Tarantula (Aphonopelma hentzi), which, along with about 28 other species, appears in up to 15 U.S. states at the end of summer.
As soon as high temperatures meet the first rains in late summer, the tarantulas’ mating season begins—along with a visible migration through desert regions and across roads. “They usually wait for the first autumn rain—they are very responsive to late summer warmth and increasing moisture,” explains Dan McCamish, lead environmental scientist at California State Parks, to “USA Today.” “If you’re lucky, you can sometimes see them swarming across the roads at certain times of the year.”
Why Tarantulas Hit the Road
Tarantulas are found in the wild in 15 U.S. states: Washington, Oregon, California, Nevada, Utah, Arizona, Colorado, New Mexico, Nebraska, Oklahoma, Texas, Missouri, Arkansas, Louisiana, and Florida. Outside of mating season, the animals usually remain hidden, as they are nocturnal and live in their self-dug burrows. During the breeding season, however, which typically lasts from late August to October, the males embark on an intense search for partners.
The annual migration of the Brown Bird Spider is particularly noted, appearing more frequently in eight U.S. states and Mexico in the fall. This spider is known by many different names. Texas, Oklahoma, and Missouri, among others, argue over who gets to name the tarantula. However, it is best known as the “Brown Texas Tarantula.” It is one of the most common bird spiders in the southern U.S. states and, like all other species, begins its migration in late summer.
By the way, all the animals mentioned here are actually bird spiders, not tarantulas. The exact biological differences between the various spider species and why they are often simply called “tarantulas” can be read in this article: Bird Spider or Tarantula—Is There a Difference?
Females Are More Likely to Be Found at the Burrow
The Texas Tarantula and other North American spiders migrate annually because “the male bird spiders are searching for a partner at this time of year,” says Dr. Andrine Shufran from Oklahoma State University in a press release. The director of the “Insect Adventure” experience center knows: “The mating season is determined by temperature and microclimate. It can occur earlier or later because the males wait for the right situation and signals to set out, but usually, the mating season lasts from late August to October.” During this breeding season, they court up to 100 females at once.
Therefore, males are often seen searching for partners, as females usually remain in their burrows. Male tarantulas have very little time to reproduce. Once they reach sexual maturity, they live only a few more months. In this short time, they must mate with as many females as possible, requiring a lot of walking. Female tarantulas stay in their caves and attract males with pheromones. 1
According to the organization Los Padres Forest Watch, there are a total of 29 different tarantula species in the U.S., ten of them in California alone. A female can lay between 700 and 1,000 eggs, which hatch after about six to nine weeks. If you encounter a tarantula sitting in its burrow or on a hole, it is likely a female waiting for males to mate, explains McCamish.
Tarantulas Are Shy but Defensive
If you are reminded of horror movies with spider attacks, you can rest assured. Aphonopelma hentzi and other North American tarantulas measure only a few centimeters and are considered peaceful animals despite their threatening appearance. Only their legs, up to 15 centimeters long, make them about palm-sized. Therefore, they are far from being as large as the largest spider in the world—and are rather shy when they encounter humans.
“Tarantulas can bite if they feel threatened, but they are most likely to run away,” Dr. Shufran continues. If there is no other option, they stand on their four hind legs and show their fangs. “Usually, the paths of spider and human separate without anyone getting hurt. As a last resort, tarantulas do bite.” But this bite is only dangerous if one is allergic to it. Typically, a cold pack is enough to treat a Texas Tarantula bite.
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Texas Tarantula Creates a Shield with Irritating Hairs
So, if you let a male tarantula go its way, you shouldn’t have a problem with the animals. However, there are spider enthusiasts who try to pet the fluffy-looking tarantulas. Or even capture them to keep them in a home terrarium.
However, this is not advisable, as the Texas Tarantula, in addition to its bite, has a very effective defense strategy. What makes them look fluffy are irritant or urticating hairs, which they use as a defense mechanism. “When disturbed, they release these itchy hairs by rubbing their two hind legs against the hairs, creating a kind of force field,” Shufran explains. “The hairs are carried by air movement and itch humans and animals immensely. You can easily tell the stress level of a bird spider by how bald the itch spot is.”
Why Tarantulas Are Important to the Ecosystem
But not only for this reason should you not disturb or remove the shy animals from nature. Like many other wild animals, they suffer from habitat loss due to settlement and agriculture. They are losing more and more retreats where they are not disturbed by humans and could fulfill their role in the ecosystem. Especially during migration time, they are often run over or the more relaxed males are poached for the pet trade and breeding.
Tarantulas serve an important function in the ecosystem as ground dwellers. They are effective hunters and help maintain balance in the insect world. Their diet includes beetles, grasshoppers, crickets, and smaller spider species. By controlling these populations, they prevent overpopulation and contribute to biodiversity.
At the same time, tarantulas themselves are a food source for many other animals—including snakes, birds, mammals like shrews, and certain wasp species that specialize in spiders. Their retreat or disappearance would have noticeable effects on several food chains. It is all the more important to not only respect the shy animals but also protect their habitats.