Disclosed herein are isoxazoline compounds of formula (Ia), wherein the variables are as described herein in free form and in salt form, an example being N-(2-((cyanomethyl)amino)-2-oxoethyl)-5-(5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)-2-methylthiophene-3-carboxamide. Also disclosed are compositions comprising the compounds and the use of the compounds in the control of parasites, in particular ectoparasites, in and on warmblooded animals.
