Stings and bites from Insects:

The poisons or venoms injected by insects, snakes, spiders and some marine creatures have been categorized by chemical composition into three main types. Defensive poisons are used to discourage intruders from disturbing nests, hives or young, or for self defense. Offensive poisons are used to disable or kill a potential meal. And anticoagulants are designed to prevent a victim’s blood from clotting after being bitten so the insect or arachnid can drink it.