A tarantula rising is about to happen in Colorado, sure to surprise unwitting campers in some parts of the state.

Each year, thousands of male tarantulas start marching around the southern part of Colorado from late August through October, according to Colorado State University’s College of Agricultural Sciences. The first tarantulas to appear show up in southeastern Colorado around the end of August, roaming throughout the month of September.

A second, southwestern wave appears a bit later, peaking in October. These tarantulas will roam around looking for a mate and after mating, they’ll die – typically at the hands of their mate or due to cold weather.

Spiders of Unusual Size are closer than (and maybe not who) you think

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

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

While this phenomenon is annually predicted, outside factors can impact tarantula numbers and where the tarantulas can be found. At night, a spotlight can help you find the spiders while they’re on the move, with each tarantula capable of wandering up to half a mile each day, according to Brent Hendrixson, a professor at Mississippi’s Millsaps College, in a Durango Herald story.

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