Agelenopsis aperta

Agelenopsis aperta, also known as the desert grass spider or funnel-web spider, is a species of spider belonging to the family Agelenidae and the genus Agelenopsis. It is found in dry and arid regions across the southern United States and into northwestern Mexico. Their body is about 13–18 mm long and they have relatively long legs in order to run after their prey. Desert grass spiders can withstand very low temperatures even though they do not cold harden. It constructs the characteristic funnel-shaped webs in crevices where the funnel will fit, where they wait in the tube for prey which they can run after using their long legs. They often hunt for their prey at night.

A. aperta is known for its territoriality and will fight intruders to protect their space. A. aperta are mainly monogamous, and the male performs an elaborate courtship ritual that involves swaying his abdomen and releasing pheromones. The male's pheromones induce a cataplectic state in the female, and then once the female is active again, they begin to mate. Desert grass spiders inject venom into their prey which results in rapid paralysis. Bites to humans, however, are not well-studied and are currently considered harmless. The agatoxin present in its venom has been researched extensively and is known to block calcium channels.