Distributional Evidence for Thermal Melanic Color Forms in Philaenus spumarius, the Polymorphic Spittlebug

In North America four of five dark color forms of the spittlebug Philaenus spumarius L. (Homoptera: Aphrophoridae) are more common in northern parts of its range. The combined frequency of these four forms (lateralis, flavicollis, leucocephalus and leucophthalmus) is negatively correlated with September temperature and, for a given latitude, cooler sites tend to exhibit higher frequencies. It is suggested that selection for thermal melanism has influenced the distribution of these forms. The fifth dark form (marginellus) increases in frequency toward the S.