This invention provides for dimericl-arylpyrazole compounds, of formulas (I),(II), and or salts thereof, and the useof these compounds against ectoparasites such as insects, arthropods andacarina. The resulting compounds may be used in veteri-naryformulations such as, for example, spot-on and pour-on formulations, which maybe used for treatment, controlling and pre-ventingof parasitic infections in warm-blooded animals and birds.
