Mexican red-leg tarantula. The Mexican red-leg, or redknee, tarantula (Brachypelma smithi) is a spider that preys on insects, rodents and small birds. It stalks its prey, before leaping onto it and pumping venom into the prey's body through its fangs. The venom liquifies the internal organs, which the spider then sucks out. When not hunting for food, the tarantula spends its time hiding from predators. Defences include kicking irritating hairs at attackers, running away or, as a last resort, biting the predator.