For aphid larvae soldiers, home repairs are a suicide mission

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Soldier nymphs of a Japanese aphid species sacrifice their lives for the colony by discharging clot-forming bodily fluids that patch holes in the nest made by predators, scientists said.

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The Nipponaphis monzeni soldier nymphs die after draining about half of their mass or drowning in the sticky fluids, the researchers said. The ones that initially survive the altruistic process are so depleted that they cannot shed their skin and later die.

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The study results by the team, including researchers of the National Institute of Advanced Industrial Science and Technology (AIST), were published in the journal Proceedings of the National Academy of Sciences on April 15.

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“This species of aphid uses a mechanism of creating a scab not to heal wounds on their bodies but to heal the wounds in their nest. That’s interesting,” said Mayako Kutsukake, a senior researcher at the AIST, a public research organizations in Tsukuba, Ibaraki Prefecture.

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The Nipponaphis monzeni infest winter hazel trees that are often seen in parks. The aphids dwell in a pear-shaped nest called a gall that is formed on a tree branch. They suck tree sap to survive.

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Colonies generally have two types of aphids: ones that give birth and soldier larvae that provide protection and do not give birth.

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Yet, some soldier larvae emerge from their skin to grow and propagate.

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When predators, such as moth larvae, create a hole in the gall and try to enter, soldier nymphs not only fight the foe, but they also secrete concretious white bodily fluids to briskly repair the hole.

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The team examined proteins in the bodily fluids and identified the enzyme phenoloxidase, which functions to congeal and harden the fluids, much like tree resin.

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The milky body fluids turn black and become like a scab to heal the “wound” of the gall in about a month, they said.

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