Harris Bed Bug Killer with Diatomaceous Earth should be used as a rack and crevice application. When bed bugs come into contact with the powder, it begins working on their legs, feet, exoskeleton or joints. The abrasive characteristics will cause dehydration of their body fluids. Apply to bed rails, mattress seams and along baseboards. Harris Bed bug powder works best when used with other methods such as liquid or aerosol spray treatments to eliminate infestations.