Individuals belonging to species of the genus Conophthorus (Coleoptera: Curculionidae) are notoriously difficult to sex, especially if only certain parts of the beetle are available and the genitals are unidentifiable. We are presenting evidence demonstrating that rows of setae and setal characteristics at the posterior margin of tergite VII (the fifth visible tergite) can be used to sex the three Mexican pine cone beetle species Conophthorus conicolens Wood, C. teocotum Hopkins, and C. michoacanae Wood, from each other. Although the three Conophthorus are clearly described taxonomically by Wood (1977), the continued increase and development of forest plantations with a mixture of host species elucidates the importance of having reliable methods of sexing these species for purposes of researching and monitoring programs of their populations and pest management and control.