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‘Crypt keeper’ wasp brainwashes far more victims than thought

There may be honor among thieves, but there certainly isn’t among parasitic wasps. A new study suggests the crypt keeper wasp, whose larvae burrow into the bodies of other wasps and live off their corpses, has more than half a dozen hosts—or, if you prefer, victims.

Those victims are typically Bassettia pallida wasps, which lay their eggs in the stems and branches of oak trees, forming swollen bumps called galls or crypts. The crypt keeper wasp (Euderus set) then lays her eggs in the gall, where her larvae either camp out next to the host hatchlings or burrow into their bodies.

When a hatchling is ready to chew its way out of the gall, the crypt keeper—through a feat of undiscovered mind control or through simply weakening the host—makes it chew a hole that is too small. That causes the host’s head to get stuck like a cork in a wine bottle. After snacking on the body of the host, the crypt keeper wasp escapes the gall by burrowing out through its host’s head, which is much softer than the tough stem of the plant.

To find out how many hosts this “hypermanipulator” has, researchers collected more than 23,000 galls containing more than 100 species of oak gall wasps—and some crypt keepers. They raised the wasps and found crypt keepers parasitizing 305 wasps from six different species, they report today in Biology Letters.

The unlucky host wasps weren’t all closely related (they came from five different genuses), but the researchers found that the crypt keeper wasp does seem to have a preferred type of gall: those that aren’t covered in fur or spikes.