In general, the venom is fast-acting, allowing for effective prey capture; however, as a general rule, scorpions kill their prey with brute force if they can, as opposed to using venom. It is also used as a defense against predators. The venom is a mixture of compounds (neurotoxins, enzyme inhibitors, etc.) each not only causing a different effect, but possibly also targeting a specific animal. Each compound is made and stored in a pair of glandular sacs and is released in a quantity regulated by the scorpion itself. Of the 1,000+ known species of scorpions, only 25 have venom that is deadly to humans; most of those belong to the family Buthidae (including Leiurus quinquestriatus, Hottentotta spp., Centruroides spp., and Androctonus spp.).