Every year in South Eastern Colorado there is a migration of Oklahoma Brown Back Tarantulas.  These are 8-10 year old males looking for a mate.  The females are in burrows in the grasslands. Once the males have mated they are usually dead by November because of cold exposure.  They are docile for the most part.  Their bite is not poisonous but if bitten one could get infected.  They also have hairs on their abdomens that can be “sprayed” at an attacker.  The hairs are irritating.