The invention relates to pyridylidene compounds of formula (I), to the enantiomers, diastereomers and salts thereof and to compositions comprising such compounds. The invention also relates to methods and uses of these N-substituted pyridylidene compounds, and of compositions comprising thereof, for combating and controlling animal pests. Furthermore the invention relates also to pesticidal methods of applying such N-substituted pyridylidene compounds. The N-substituted pyridylidene compounds of the present invention are defined by formula I, wherein X, Het, R1, R2, R3, R4 and R6 are defined as in the description.