Certain new benzoyl chloride (fluoroalkylphenyl)-hydrazones have been found to be active against arthropod pests and worms. The characterizing fluoroalkyl group on the phenylhydrazone ring can be associated with other substituent atoms and groups. The benzoyl ring can also be substituted. Representative substituent atoms and groups include the halogen atoms, lower-alkyl groups, lower-alkoxy groups, and a nitro group. The fluoroalkyl group is more meaningfully designated an '''' Alpha -Fnalkyl'''' group because fluorine atom substitution on the Alpha -carbon appears to be advantageous. The new compounds can be prepared by reacting a benzoic acid 2( Alpha -Fnalkylphenyl)hydrazide with phosphorus pentachloride to obtain a benzoyl chloride ((dichlorophosphinyl- Alpha Fnalkyl)phenyl)hydrazone that is reacted with phenol to produce the desired benzoyl chloride ( Alpha -Fnalkylphenyl)hydrazones. The compounds having chlorine on the phenylhydrazone ring can be prepared by direct halogenation of benzaldehyde ( Alpha Fnalkylphenyl)hydrazones or a benzoyl chloride ( Alpha Fnalkylphenyl)hydrazone. Methods of anti-arthropodal use and novel formulations adapted for biological use of the new compounds are also described.