One reason insects breath differently than we do is that the surface to volume ratio between us is so different. Naturally, volume increases as the cube of the

One reason insects breath differently than we do is that the surface to volume ratio between us is so different. Naturally, volume increases as the cube of the linear dimensions of the organism and the surface area only increases as the square of the dimension. This means that the ratio S/V is directly proportional to the size of the organism. A mouse has a much lower terminal velocity when falling than a human, for example, because they have a higher surface to weight ratio (weight of course is related to volume). Insects are so small that breathing doesn't require the mechanisms that we require because their S/V ratio is so so much larger. On the other hand, desiccation is a much greater problem for insects as is surface tension when wet. For these reasons, insects often have waxy coatings or other means of protecting themselves from drying out or being trapped in by a water drop, but an ant doesn't have to worry about falling out of a tree.