Finding: More than 300 million years ago, there was 31 to 35 percent oxygen in the air. That means that the respiratory systems of the insects could be smaller and still deliver enough oxygen to meet their demands, allowing the creatures to grow much larger.
A recent study was conducted to help determine why insects, once dramatically larger than they are today, have seen such a remarkable reduction in size over the course of history. Insects breathe through a network of air filled tubes that deliver oxygen directly to the cells. These tracheal tubes, especially in the leg, take up more room in larger beetles.
There were hundreds of ideas to explain the small size, but none of them could be proven. One theory was that it was an insect’s respiratory system that limited its size. So a study was launched an extensive study using beetles and fruit flies.
The study, much of which was performed at Illinois’ Argonne National Laboratory, involved the examination of various beetles’ respiratory systems, using new x-ray beam technology to help determine how they breathe.