Spiders are venomous to insects. Actually, that venom is basically saliva, if I remember correctly, designed to digest the prey not to kill it (like us, spiders digest in part outside of their body - we cook, they inject their saliva).
> Of around 50,000 spider species known, only about 25 (1/20 of 1%) have venom capable of causing illness in humans
Virtually all spiders are venomous, but many can't penetrate human skin and many have venom that isn't dangerous to humans at the dosage injected.