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Nature Notebook – Wasp Ovipositors

Butterfly House visitors are a bit intimidated by the large wasps buzzing about until we assure them that they are male cicada killer wasps. Males don’t lay eggs, so they don’t have ovipositors. No ovipositor means no “stinger.”

The sharp, pointed ovipositors of some species of wasps are used by females to lay eggs inside living organisms which will become food for the wasp larvae. However, those organisms fight back, so the wasps developed paralyzing venom to accompany the egg insertion. The venom also proved to be a potent defensive weapon.

The ovipositor is a three-pronged tool (two lancets and a stylet) in a shaft which sits inside the abdomen casing until needed. The two halves of the casing open slightly to project the shaft. When the shaft is plunged into the victim, the barbed lancets rapidly move up and down within the stylet to open the wound and anchor the shaft. Muscles around the connected venom sac contract to pump the venom down and out through the shaft tip into the wound.