what is poison sting

I think it is a poisonous sting not as poison sting,,,,,,,,,,,,,,,,

So, Poisonous sting means,

Some plants defend themselves even more aggressively. They sting. The nettle's sting is a modified hair. Its tip is a minute glassy needle which if given even the slightest touch, breaks off. The broken edges are so sharp that they can cut skin. At the same time a poison held in a small chamber at the bottom of the hair squirts into the wound. The poison [formic acid] causes us considerable pain.