Darwin predicted it. But like his theory of evolution, it had many critics. He suggested that many insects wanted to leave the flight and settle on the ground. His ideas were rejected. But now the insects that have lost the ability to fly confirm this.
On some small islands halfway between Antarctica and Australia what Darwin suggested happens. Flies run and moths crawl on the ground. Like them, many of the insect species living there have lost their ability to fly.
Darwin knew of a similar case in Madeira, where many bugs had stopped roaming the sky. It was easy for the biologist. Wind is not a good friend of flying insects on an island. If they venture a little, they may end up in the middle of the ocean with no way of returning home. “Those who stay on site to produce the next generation are more reluctant to take off. Evolution does the rest, ”says Rachel Leihy. He is from the Faculty of Life Sciences at Monash University.
The famous botanist Joseph Hooker had visited the sub-Antarctic Kerguelen Islands. In his letters to Darwin he had commented on the strange number of beetles and moths that did not fly. However, he believed the wind hypothesis was wrong. It did not explain the large proportion of flightless insects found in continental environments such as deserts.
However, these sub-Antarctic islands are located in two areas with strong south winds. The Marion Islands and Heard Island have a remarkable number of flightless insect species compared to others. “Almost half (47%) of the insect species on the islands of the Southern Ocean have lost their ability to fly,” says Leihy.
“Some flightless species have completely lost their wings. However, many still have them. They are very short and cannot be used for flying. “The study was published in the journal Proceedings of the Royal Society B.”
The team tested various hypotheses to explain the loss of flight ability. For example: In places where there are fewer predators, flight may be less beneficial than in places where there are many predators to avoid. In cold environments such as mountain tops, flying can also be too energy-intensive.
‘We tested all the alternative hypotheses for the Southern Ocean. We found that wind speed is the best indicator of the number of flightless insect species on these islands, ”says Leihy. Wind conditions make it difficult for insects to fly. And energy is expensive. Therefore insects no longer invest in flight and divert resources for reproduction. As the researcher notes, “It is extraordinary that after 160 years, Darwin’s ideas continue to add knowledge to ecology.” Point for insects that have lost the ability to fly: Darwin would thank them.