Ethylene derivatives of formula (I): ##STR1## where Q is an unsubstituted or substituted phenyl or heterocyclic group, especially a 4-thiazolyl, 1- or 3-pyrazolyl, 1,3-oxazol-4-yl, phenyl or pyridyl group; E is a substituent such as a cyano group; A is a substituent such as a 4-pyrazolyl or thiazolyl group; and B is a substituent such as an alkylcarbonyl group. Agricultural chemicals and agents for preventing the attachment of aquatic organisms containing one or more such ethylene derivatives.