Compounds having the formula ##STR1## in which R.sub.1 is methyl or ethyl; R.sub.2 is C.sub.1 -C.sub.6 alkyl; R.sub.3 is hydrogen, halogen or methyl; and R.sub.4 is hydrogen, methyl or phenyl; or R.sub.3 and R.sub.4 taken together form a tetramethylene chain; provided that R.sub.3 and R.sub.4 are not both hydrogen, are insecticides and/or nematicides.