A SoCal beetle masquerading as an ant may answer an important evolutionary question

The Angeles National Forest ranger is not a 500-pound black bear or a mountain lion.

A small ant.

The softwood ant forms “a multimillion-strong community insect carpet that spans the mountains,” says Joseph Parker, professor of biology and director of the Center for Evolutionary Sciences at Caltech. Their large colonies influence how quickly plants grow and the size of other species. That much, scientists already know.

Now Parker, who has spent 8 years in his lab studying red and black ants, believes they have found something that helps answer an important question about evolution.

In a paper published in the journal “Cell,” they describe the remarkable ability of one species of insect to live among fighting ants.

beetle, Sceptobius lativentriseven smaller than an ant, it turns off its pheromones to hide. Then the beetle looks for an ant – it climbs on top of it, puts its antennae in its jaws and releases its pheromones with its brush-like legs. It applies ant pheromones, or cuticular hydrocarbons, to itself as a kind of mask.

Ants mark their nests with these chemicals. So when a person comes to a beetle wearing its own chemical suit, so to speak, it accepts it. The ants even feed the beetles mouth to mouth, and the beetles eat the eggs and larvae of their group.

However, there is a hitch. Cuticular hydrocarbons have another function: they form a waxy barrier that prevents the beetle from drying out. Once the beetle has turned off its pheromones, it cannot turn them back on. That means that if it is separated from the ants it plays with, it is a goner. They need to avoid decay.

“So the kind of behavior and molecular biology that is required to integrate the beetle into the nest is the very thing that prevents it from leaving the colony,” said Parker, who describes it as a “Catch-22.”

The findings have implications beyond the insect kingdom. It provides a basis for “grounding,” Parker said. In other words, when a close symbiotic relationship forms – where at least one organism depends on the other for survival – it is locked in. There is no turning back.

Parker, speaking from his office, which is decorated with white pictures of rove beetles — his lab’s main focus — said it pays to explore “the obscure branches of the tree of life.”

“Sceptobius he’s been living in the forest for millions of years, and people have been living in this part of the world for thousands of years, and it just took a 20-minute drive into the forest to find this amazing evolutionary story that tells you so much about life on Earth.” “And there must be many, many other stories just in the woods up the road.”

John McCutcheon, a biology professor at Arizona State University, studies the relationship between insects and the invisible bacteria that live inside their cells. So for him, the main characters in the latest paper are really big.

McCutcheon, who was not involved in the new research, called it “cool and interesting.”

“It raises a model, which I think is happening in other programs,” he said. “But I think its strength is that it involves actors, or living things, that you can see,” which makes it less complicated and easier to understand.

Now, he said, people who study even small things can test the proposed model.

Noah Whiteman, a professor of cell and molecular science at UC Berkeley, praised the paper for breaking the symbiotic relationship that has taken scientists. People knew them Sceptobius he was able to pretend to be an ant, but they didn’t know how to get it out.

“They’re taking this program that has long been a natural history curiosity, and they’re taking it forward to try to understand how it evolved using the latest molecular tools,” he said, calling the work “beautiful and beautiful.”

As for the broader claim – that highly dependent relationships are dead ends, evolutionary speaking, “I would say it’s still an open question.”