Pesticidal compounds of formula II: R.sub.A CR.sub.3 .dbd.CR.sub.4 CHDR.sub.Bin which formula:R.sub.A represents a group ArCR.sub.1 R.sub.2 - in which Ar represents a phenyl or naphthyl group optionally substituted by one or more halogen, alkoxy, haloalkoxy, methylenedioxy, C.sub.1 -C.sub.6 alkyl or haloalkyl groups;R.sub.1 and R.sub.2 together with the carbon to which they are attached represent a C.sub.3 -C.sub.6 cycloalkyl group optionally substituted by one or more halogen atoms or C.sub.1 -C.sub.6 alkyl groups.R.sub.3 and R.sub.4 which may be identical or differ, represent hydrogen halogen or C.sub.1 -C.sub.6 alkyl groups andR.sub.B represents the residue of an alcohol R.sub.B CHDOH in which D is hydrogen or cyano and of which the [1R, cis] 2,2-dimethyl-3-(2,2-dibromovinyl) cyclopropane carboxylic ester is significantly insecticidal,the configuration of R.sub.A and CHDR.sub.B about the double bond being mutually trans,and processes for the production of compounds I, intermediates, pesticidal compositions comprising I, processes for the production thereof, methods for controlling pests, especially rice pests, in which such compounds are utilized and the use of compounds I for the manufacture of a pesticide.