Bithienyl compounds of the following structural formula are phototoxic insecticides and acaricides: ##STR1## wherein R.sub.1 is selected from hydrogen, halogen, alkyl, haloalkyl, alkoxy, and haloalkoxy; R.sub.2 is selected from hydrogen and halogen; R.sub.3 is selected from hydrogen, alkyl, phenyl, and thienyl; and R.sub.4 is selected from hydrogen, halogen, alkyl, and haloalkyl.