A compound of formula (I): wherein A1, A2, A3, A4, A1′, A2′, A3′, A4′, A5′, A6′, G1, R1, R2, R3, R4, R5a and R5b 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) or compounds of formula (I′), to insecticidal, acaricidal, nematicidal and molluscicidal compositions comprising compounds of formula (I) or compounds of formula (I′), and to methods of using compounds of formula (I) or compounds of formula (I′) to combat and control insect, acarine, nematode and mollusc pests.