This is a female Pelecinid wasp, and NO, that is not a stinger! It is her long abdomen which is used to lay eggs, and the way she does this is pretty interesting. Especially if you are a gardener with a grub problem. She uses that abdomen to probe into the soil and when she feels a grub, she lays an egg, and does this over and over, one egg per grub. The eggs hatch and the larvae parasitize the grubs, killing them. The adults, the wasps,do no damage whatsoever to anything or anyone. Indeed, they are very beneficial insects, so next time you see one of these, instead of fearing them, welcome them!