Coumaphos is a nonvolatile, fat-soluble phosphorothioate with ectoparasiticide properties: it kills insects and mites. It is well known by a variety of brand names as a dip or wash, used on farm and domestic animals to control ticks, mites, flies and fleas.[1]
It is also used to control Varroa mites in honey bee colonies, though in many areas it is falling out of favor as the mites develop resistance and as the residual toxicity effects are becoming better understood.[2][3]