The female-produced sex pheromone of the scarab beetle Phyllophaga lanceolata was identified as the methyl ester of an essential amino acid, L-leucine. During field testing, 239 male P. lanceolata were caught in traps baited with L-leucine methyl ester. L-Isoleucine and L-valine methyl esters, similar in structure to L-leucine methyl ester and previously identified as female-produced sex pheromone compounds employed by other Phyllophaga species, were also tested. Addition of L-valine or L-isoleucine methyl esters to the L-leucine methyl ester in 1:1 ratios completely inhibited attraction of P. lanceolata males. Males of P. squamipilosa were also captured using L-leucine methyl ester. This is the first record of P. squamipilosa from Kansas.