Make sure you keep those tents zipped up at night. A storm of tarantulas is about to start marching around Colorado in search of mates, sure to shock campers in some parts of the state.

Each year, 10,000s of male tarantulas start marching around the southern part of Colorado, typically from late August through October as summer nighttime temperatures cool.

Generally, the first tarantulas to appear will show up in southeastern Colorado around the end of August, roaming throughout the month of September. A second, southwestern wave tends to appear a bit later in the year, with their presence peaking in October. These fuzzy fist-sized arachnids creep around on a quest to find a mate and after mating, they’ll die – typically at the hands of their mate or due to cold weather.

According to The Denver Channel, one of the best places to see these tarantulas is at Comanche National Grassland near La Junta, Colorado. This is located in southeastern Colorado, so visitors can expect a mid-September peak.

Two additional spots to see this natural phenomenon include just north of Ordway on Highway 71 and between La Junta and Kim on Highway 109, according to the La Junta Tribune-Democrat.

Remember, while this phenomenon is predicted to occur, outside factors can impact tarantula numbers and where the tarantulas can be found. At night, a spotlight can help spiders-spotters find tarantulas while they’re on the move, with each tarantula capable of wandering up to half a mile each day. It can sometimes take awhile or a couple trips to find these traveling hordes, but once they’re found, the scene can be truly shocking.

While tarantulas don’t pose much of a threat to humans, it is important that curious members of the public avoid interfering with this natural and important behavior in any way. While tarantulas typically can’t do much damage to humans, they can throw irritating hairs at potential threats and deliver a painful bite that’s often compared to a bee sting.

According to a report from USA Today, male spiders can take up to 10 years to reach sexual maturity. As they attempt to find a female mating partner hidden in a burrow about a foot underneath the ground, male tarantulas use their hairs and legs to detect vibrations. Sadly, these males will mate once and die, sometimes killed by the female they mate with. Female tarantulas can live up to 20 years or more.

Five different species of tarantulas are found in Colorado, including Aphonopelma coloradanum, Aphonopelma echinum (Colorado chocolate brown tarantula), Aphonopelma hentzi (Oklahoma brown tarantula), Aphonopelma vogelae, and Aphonopelma marxi (Grand Canyon black tarantula). They tend to survive by eating beetles and insects they’re able to capture from their burrow by surprise.