Then they realized that they hadn't been paying attention to whether the grasshopper was up or down in the container that held it. Grasshoppers, like other insects, obtain oxygen through tubes or trachea that are open to the outside air and branch into smaller and smaller tubes in the insect's body. All insects have these, and some have airbags, to store and pump air, as do the grasshoppers.
It turned out that the tubes were more compressed in the lower part of the animal, because gravity was causing the grasshopper equivalent of the blood to sink in the lower half of the animal.
This is similar to what happens when humans stand up quickly and get dizzy, or the way blood reaches the head during a headstand. Humans have valves in the circulatory system to combat this problem, and their heart rate may increase, to pump blood faster.
But insects do not have the same system. A grasshopper has a heart, but it was thought that most of his body was like a large bag of blood. However, the researchers discovered that grasshoppers could substantially counteract the effect of gravity when they were conscious. When they were anesthetized with nitrogen, they couldn't.
The researchers found that grasshoppers could change the pressure in different parts of their body. And the animals were able to maintain different pressures on different parts of the body. How they do it is the next question. But they must have some way to block the abdomen of the chest, for example, to create different pressures.
The discovery reveals something new about the intersection of physics and biology. For now, it seems to be true in grasshoppers, at least, and probably in beetles, according to another study by Dr. Socha. But all insects will be subject to the same physical forces, which few scientists have paid attention to before. And it seems unlikely, said Dr. Socha, that grasshoppers are the only ones to develop coping mechanisms.
Even so, it may be that smaller insects, such as fruit flies, do not need to regulate their bodies in the same way. Dr. Hu said that ants maintain the same metabolism whether they are walking horizontally or in a straight line. Future studies will show how large the insects have these adaptations and what exactly they are.