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Worker ants had a lot to gain by losing the ability to fly

Losing the ability to fly made ants much stronger, according to a new study from Okinawa Institute of Science and Technology Graduate University (OIST). When the researchers created 3D models to analyze the muscles and internal skeletons of ants, they confirmed the theory that the loss of flight in worker ants is directly linked to the evolution of greater strength.

“Worker ants evolved from flying insects,” said Professor Evan Economo. “We’ve always assumed that losing flight helped to optimize their bodies for working on the ground, but we have much to learn about how this is achieved.”

Among flying insects, the wing muscles often occupy more than half of the thorax, which places major constraints on the muscles used to support the rest of the body. The experts speculated that once the constraints of flight were removed in worker ants, the remaining muscles in the thorax were free to expand and reorganize.

While previous studies on flight loss focused on the external structure of worker ants, the OIST researchers constructed a detailed picture of the inside of the thorax.

The researchers conducted a detailed analysis of two distantly related ant species, including both the wingless workers and the flying queens. They also confirmed the findings based on a broader sample of species.

Using advanced X-ray technology to scan the internal and external anatomy of the ants, the team confirmed that the loss of flight had allowed for the reorganization of the thorax.

“Within the worker ant’s thorax, everything is integrated beautifully in a tiny space,” said study lead author Dr. Christian Peeters. “The three muscle groups have all expanded in volume, giving the worker ants more strength and power. There has also been a change in the geometry of the neck muscles, which support and move the head. And the internal attachment of muscles has been modified.”

When the researchers studied the loss of flight among wasps, they found that the bees had responded in a completely different way. Wingless wasps are solitary and consume food on their own, while ants work in teams as part of a colony. The teams scavenge for food and carry it back to the nest for the queen and younger ants working within the nest.

Going forward, the scientists plan to develop more detailed biomechanical models of how different muscle groups function, conduct similar research on the mandible and legs, and compare the diversity among different ant species.

“We’re interested in what makes an ant an ant and understanding the key innovations behind their success,” explained Professor Economo. “We know that one factor is the social structure, but this individual strength is another essential factor.”

The study is published in the journal Frontiers in Zoology.

By Chrissy Sexton, Staff Writer

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