The sex of adults of Phenolia (Lasiodites) picta (MacLeay) is distinguished by the morphology of the pygidium and the presence of a well sclerotized tergite VIII in males. These differences are visible under a binocular microscope at a low magnification (15×). As the difference between the sexes can be distinguished without killing specimens, it can be used to observe the specific behaviors of females and males and in ecological research.