Abstract: The present invention relates to novel compounds of the formula I and the N-oxides, stereoisomers, tautomers and agriculturally or veterinarily acceptable salts thereof wherein C1 is C or CH; C2 is C or CH; A1 is N or C; A2 is N, C(R2), N(R3), O, S or C(R4,R5); and A3 is N, O, S, N(R6), C(R7) or C(R8,R9); where one or two non-adjacent bonds in the 5-membered ring formed by C1, C2, A1, A2 and A3 are double bonds, while the others are single bonds, provided that the bond between A1 and A2 or the bond between A1 and C1 or the bond between A2 and A3 or the bond between C1 and C2 or the bond between A3 and C2 is a double bond further provided that at least one of A1, A2 and A3 is N, N(R3) or N(R6), and where Ar, R1, R2, R3, R4, R5, R6, R7, R8, R9 and (R)k are as defined in the claims and in the description, which are useful for combating or controlling invertebrate pests, in particular arthropod pests and nematodes.