Only honey bees have serrated stings, and only the workers at that. Serrated stings stick in the skin of birds and mammals and are thus torn out, so they are only stung when the nest as a whole is threatened. Queen bees have smooth stings like wasps, so can sting many times. The serrations are thought to enhance the sting's ability to pierce insect exoskeletons, useful for bee-to-bee combat.
Solitary bees can sting as many times as they like. If they have a sting, that is. Many do not.
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