Natures wonders: using fungus to fight wasps (Introduction)

by David Turell , Thursday, May 09, 2024, 18:26 (11 days ago) @ David Turell

Stink bugs grow fungus on their legs:

https://www.newscientist.com/article/2429711-stink-bugs-grow-a-fungal-garden-on-their-l...

"Female stink bugs have a bizarre organ that they use to cultivate a garden of fungi, which in turn helps protect their eggs from a species of parasitic wasp.

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"The researchers were looking at how females use the tympanal organ in their hind legs, a kind of eardrum that insects use to hear sounds, during mating. They found the females had a small, porous indent in their legs, full of fungal tendrils called hyphae. Each female had cultivated multiple fungal species within this organ, with a surprising amount of diversity.

"What’s more, this was no accidental growth. As the females deposited their eggs, they scratched at the fungal-filled pores with the claws of their other leg, then rubbed the eggs with their claws, smearing them in fungi. Within a few days, the eggs were completely covered in the hair-like hyphae. When the young nymphs hatched., they retained this fungal coating until they moulted.

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"The mystery deepened until the researchers studied stink bug eggs in the wild and found they were frequently parasitised by a previously undescribed wasp, now named Trissolcus brevinotaulus. They discovered that the wasp lays its eggs inside the stink bug eggs, but is thwarted when the hyphae are thick enough. The wasps have their own trick, however, as the females have thicker antennae than the males, which may be used for breaking through this thicket of hyphae to lay their eggs, according to the team.

“'I’ve never seen a true bug [the order that stink bugs belong to] use fungus this way,” says Nikolai Tatarnic at the Western Australian Museum in Perth. “Egg parasitism is a huge risk to many insects, especially those whose eggs are laid exposed, as opposed to buried in soil or in plant tissue,” he says. “I’m sure that after reading this, all the bug people will be looking through their dinidorid [the family stink bugs belong to] collections and looking again at the tympanal organs of the females.”

"He says there is a precedent for a similar egg protection strategy, though. “Various assassin bugs that hunt using plant resins have been shown to store resin, which they also use to coat their eggs – much in the same way as these stink bugs.'” (my bold)

Comment: a learned instinct or a designed action? Since the activity is seen in several types of insects and such activity would protect species from extinction, i believe it is a designed instinct. How would a species survive with totally unprotected eggs?