 Under experimental conditions, when spiders were injected in the leg with bee or wasp venom, they shed this appendage.But if they are injected with only saline, they rarely autotomize the leg, indicating it is not the physical insult or the ingress of fluid "per se" that causes autotomy.Spiders injected with venom components which cause injected humans to report pain (serotonin, histamine, phospholipase A2 and melittin) autotomize the leg, but if the injections contain venom components which do not cause pain to humans, autotomy does not occur.