Kids of wasp-cannibals eat their siblings because nature is cruel

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If you are growing baby wasps with a voracious appetite and a declining supply of insect carcasses for food, home delivery is not an option. Your next meal is something that is nearby in your closed nursery, and for some larvae this means that tomorrow’s dinner will probably be their closest brother or sister.

Scientists have recently reported that sibling cannibalism is surprisingly common in larvae of this species Isodontia Harmandi, a type of solitary wasp that does not live together in hives. Most likely, individual females create nurseries in the cavities of plants found in nature, laying about a dozen eggs in the bodies of paralyzed insects, which the larvae then consume after hatching. Having laid eggs, mother wasps kill in children’s still victim of insects and seal up an entrance with pieces of a moss.

After children hatch and gnaw on the carcasses of insects, an even more horrific event occurs: some of the larvae begin to devour their siblings, according to a new study.

Between 2010 and 2015, researchers collected and analyzed more than 300 I. Harmandi nests in central Japan, counting the number of eggs, larvae and cocoons to determine the size of the brood, and then record the status of the brood at different stages of development. They ruled out nests in which larvae were killed by predator attacks or environmental factors such as mold, and they found that otherwise “healthy nests” brood size, however, decreased from 41% to 54% on average between stages. eggs and cocoon formation.

The researchers then reared the larvae in 39 nests and found a reduction in brood in approximately 77% of the nests at the larval stage and in approximately 59% of the nests after the cocoon stage.

Finally, they used slow-motion video recordings to monitor the development and behavior of larvae in 19 nests, and they saw that sibling cannibalism occurred in 74% of them, said study co-author Tomodi Endo, Honored Professor of the Cobe School of Humanities at the University. . in Japan, Live Science reported in an email. Cannibals tended to be larger than the siblings they ate, and victims were often just hatched or still very small and clung to insect victims, although sometimes both larvae were “medium-sized,” according to the study.

In one case, a group of larvae were already eating insect food when one of the children started biting a brother and sister who was participating in the festivities.

Previously, most breeding reduction studies have looked at the process in birds, but the findings of scientists suggest that breeding reduction through cannibalism is a common occurrence in I. Harmandi nurseries, and this could be the result of “mother wasp overproduction,” Endo said. In other words, female wasps lay too many eggs for all the larvae to survive on the insect carcasses she gives, leaving her babies with no choice but to cannibalize each other, Endo explained.

Researchers were surprised not only by how often Isodontia Harmandi the larvae cannibalized their siblings, as well as how calmly they did so, chewing their unfortunate victims “without any apparent aggression,” Endo said.

“Of course, this is just our impression,” he added.

As for when and how wasp larvae “realize” that their initial food supply is running out and that cannibalism is the best option for their survival, this is one of [the] topics in our next work, ”Endo said.

The findings were published May 18 in the journal PLOS One.

Originally published on Live Science.

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