A compound of formula (I) wherein A1, A2, A3, A4, R1, R2, R3 and R4 are as defined in claim 1; or a salt or N-oxide thereof. Furthermore, the present invention relates to processes and intermediates for preparing compounds of formula (I), to insecticidal, acaricidal, nematicidal or molluscicidal compositions comprising them and to methods of using them to combat and control insect, acarine, nematode or mollusc pests.