Mites Repay their Host by Offering Protection from its Rival

By Andrew Moseman | July 7, 2008 6:05 pm

Potter wasps get protection from their mite parasites.Even parasitic mites, it seems, have something to offer.

Scientists had long known that a parasitic mite lived on potter wasps and survived by dining on the wasp’s hemolymph, a fluid found in many invertebrates that functions in their circulatory system similarly to how blood does in ours. They didn’t know why the potter wasps would not only tolerate this intrusion but also encourage it—the wasps have a kind of natural pocket to carry the mites around. In a study published in the Proceedings of the Royal Society B, Japanese researchers say they’ve found out what potter wasps get out of this arrangement: Protection.

A different wasp—a parasitic one—likes to invade the potter wasp’s nests, kill the larvae, and plant its own eggs. But the mites are the potter wasps’ mercenaries. When a parasitic wasp comes to the nest, the mites attack, and though they aren’t particularly well-adapted for combat, a large enough group can hurt a wasp enough times to kill it. The researchers say that in their study, a gang of six mites would kill a parasitic wasp about 70 percent of the time; 10 or more mites working together made the kill every time.

The mites, researchers say, have never been known to attack any other creature. But it should come as no surprise that they’re willing to go to war in this instance: By killing the invaders and protecting young potter wasps, the mites are just looking out for their own children that will eventually live on those young wasps.

The wasp-mite partnership isn’t the only example of the natural world resembling a mafia operation. In June we wrote about ants that, as a part of a three-way partnership with aphids and milkweed, fight off caterpillars and other creatures that would love to eat the plant. Just goes to show the wisdom of having powerful friends.

Image: iStockphoto

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