Desiccants function by:

Desiccants function primarily by absorbing moisture and dehydrating pests. This mechanism is effective because desiccants, such as diatomaceous earth or silica gel, work by drawing moisture out from the bodies of insects. As these pests come into contact with the desiccant, the moisture is removed, leading to dehydration and ultimately death. This method of pest control does not rely on toxic chemicals but rather on the physical property of the desiccant to disrupt the pest's ability to maintain hydration, which is critical for their survival.

In contrast, the other options do not accurately describe the function of desiccants. Increasing moisture would create a more hospitable environment for pests, while relieving insect nervous system functions and encouraging pest growth would not contribute to pest control and may even exacerbate pest problems. Understanding the role of desiccants in pest management emphasizes the importance of moisture control in eliminating unwanted pests.