Bed Bugs Fear Water, Study Reveals

Bed bugs are notorious pests that evoke fear, and for good reason. Once they invade a home, they can be extremely challenging to eradicate. However, recent research has uncovered an unexpected weakness of these pesky insects—water and damp surfaces.

A study from the University of California, Riverside, published in the Journal of Ethology, highlights this newfound aversion. Dong-Hwan Choe, an entomology professor involved in the research, explains that this finding aligns well with the bed bug’s unique body structure.

Bed bugs are notably flat and possess small openings called spiracles on their bellies. Choe points out that if they come into contact with water, they risk getting stuck and blocking their respiratory openings. “Water could be quite lethal from a bed bug’s viewpoint,” he notes, emphasizing that their avoidance of moisture makes complete sense.

This revelation came about somewhat accidentally in the Choe lab. Typically, bed bugs are kept in vials, and the researchers use an artificial feeder to provide them with blood. The bugs crawl up, extending their mouthparts through a membrane to feed.

One day, a small tear in the membrane caused blood to leak and wet some paper in the vials. Choe initially thought the bed bugs would take advantage of this opportunity to feed from the soaked paper. “But they did the opposite,” he recalls. “They actively avoided the wet parts of the paper, refusing to approach the areas that got wet.”

To further investigate, the researchers also wet the paper with plain water and observed similar behavior. Inspired by these findings, one of Choe’s postdoctoral researchers, Jorge Bustamante, devised a series of experiments. Using a specialized infrared camera paired with video analysis software, Bustamante could track the tiny movements of the bed bugs, which are often less than 2 millimeters long.

The results confirmed that all bed bugs—regardless of gender or age—steered clear of wet surfaces. Interestingly, younger bed bugs were quicker to turn away upon encountering moist areas, suggesting they might be more sensitive to dampness.

While this behavior might be surprising, it could have practical implications for pest control. Understanding that bed bugs avoid wet surfaces could guide the creation and effectiveness of water-based insecticides. If these sprays don’t immediately kill the bugs, they might simply retreat to other, drier areas of an affected property.

Choe offers a straightforward piece of advice for anyone worried about having bed bugs on them. “Take a bath. It’ll help,” he suggests. Although, as he notes, dealing with bed bugs in a room requires a different strategy.

For more detailed insights, refer to the study by Jorge Bustamante et al., titled “Behavioral response of bed bugs (Hemiptera: Cimicidae) to wet surfaces,” published in the Journal of Ethology (2025).