The present invention relates to novel fused tricyclic 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 C 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. The compounds of formula (I), as well as the N-oxides, stereoisomers, tautomers and agriculturally or veterinarily acceptable salts thereof, are useful for combating or controlling invertebrate pests, in particular arthropod pests and nematodes. The invention also relates to a method for controlling invertebrate pests by using these compounds and to plant propagation material and to an agricultural and a veterinary composition comprising said compounds.La présente invention porte sur de nouveaux composés tricycliques fusionnés représentés par la formule (I) et leurs N-oxydes, stéréoisomères, tautomères et sels acceptables en agriculture ou sur le plan vétérinaire, dans laquelle formule C représente C ou CH C2 représente C ou CH A1 représente N ou C A2 représente N, C(R2), N(R3), O, S ou C(R4,R5) et A3 représente N, O, S, N(R6), C(R7) ou C(R8,R9) une ou deux liaisons non adjacentes dans le noyau à 5 chaînons formé par C1, C2, A1, A2 et A3 étant des doubles liaisons, alors que les autres sont des liaisons simples, à condition que la liaison entre A1 et A2 ou la liaison entre A1 et C1 ou la liaison entre A2 et A3 ou la liaison entre C1 et C2 ou la liaison entre A3
