AbstractThe insecticidal activities to houseflies and to mustard beetles of the 19 methylbenzyl (±)‐cis‐trans‐chrysanthemates were measured to establish the patterns of substitution that produce the greatest toxicities to these insects. The two species of insect differ in their responses to the various compounds in the series. The most active compounds to houseflies and mustard beetles are, respectively, 2,4,6‐and 2,3,6‐trimethylbenzyl (±)‐cis‐trans