ABSTRACT Relative attractiveness tests with the eight individual racemic isomers of trimedlure, teTt-butyl 4(and 5)-chloro-c1s-and tTans-2-methylcyclohexane-l-carboxylate (TML), showed that one of the four cis isomers, TML-Y (teTt-butyl c1s-5-chloro-cis-2-methylcyclohexane-I-carboxylate), was attractive to CeTatitis capitata (Wiedemann) and long lasting. The isomer is present in cis-TML in a concentration of about 5%. The three other cis isomers, which are present in about equal amounts, were unattractive. The relative attractiveness of the four tTans isomers was the same as reported previously. Possible structure-activity relationships are discussed. KEY WORDS Insecta, CeTatitis capitata, attractant, lure MALE MEDITERRANEAN FRUIT FLIES, CeTatitis capitata (Wiedemann) are strongly attracted to trimedlure, tert-butyl 4(and 5)-chloro-cis-and trans-2-methy Icyclohexane-l-carboxylate (TML), which consists of a blend of eight racemic isomers (Beroza et a!. 1961). Commercially synthesized TML contains 90-95% of the four possible trans isomers, which are designated TML-A
