London, July 8 : Japanese scientists have discovered that that potter wasps use a parasitic mite called Ensliniella parasitica as bodyguards to protect their babies from parasitic wasps.
Kimiko Okabe and Shun'ichi Makino from the Forestry and Forest Products Research Institute in Tsukuba call it a surprising discovery because the mites generally show no aggressive behaviour.
"None of astigmatid mites, which include this species, were previously known to attack other species, particularly ones larger than themselves," New Scientist magazine quoted Okabe as saying.
After breeding, potter wasps (Allodynerus delphinalis) build a nest and lay eggs inside cavities that contain food, and are sealed with mud and saliva.
Their offspring are threatened by parasitic wasps that try to invade the nest to lay their eggs inside the cavities. In the process, the baby potter wasp is killed.
The mite ensliniella parasitica is known to feed the potter wasp's haemolymph, a vital circulatory fluid that is rich in nutrients. Scientists have always thought that the mite offers nothing to the potter wasps in return.
However, when Okabe and Makino studied the behaviour of host and mite under lab conditions, they found that the mites would surround and kill a parasitic wasp when it entered a potter wasp nest.
The researchers said that the mites did not always repel an intruder successfully.
They were themselves killed of if fewer than six mites attacked an intruder, according to the researchers.
Six or more mites killed the intruder 70 per cent of the time and ten always killed it, they said.
Okabe revealed that potter wasps even have little pockets on their body called acarinaria that offer a comfy home for parasitic mites, and that each acarinaria usually contains more than six mites.
The researcher said that it was to be tested how that magic number was maintained.
A research article on the study has been published in the journal Proceedings of the Royal Society.