Removing oxygen from the bubble by metabolism decreases the partial pressure of oxygen compared to water and increases the partial pressure of nitrogen. Oxygen tends to move down its concentration gradient into the bubble while nitrogen moves down its gradient from the bubble into water. The solubilities of gases become important. Nitrogen has low solubility in water, and it diffuses out of the bubble more slowly than oxygen diffuses from the water into the bubble. This system can provide enough oxygen to small, inactive insects to allow them to remain submerged for months.
More active insects require more oxygen.
The diving beetles have to surface every few minutes to replenish their oxygen stores. In addition, certain physical parameters assert themselves. For one, as we saw earlier, water temperature effects the amount of oxygen that can be dissolved in water. At higher temperatures there is less oxygen in water, and at the same time an insect requires, and consumes, more oxygen. A physical gill may be of small value under such circumstances.