TheAnolis dewlap is a highly specialized display organ that shows considerable interspecific variability throughout the genus. Differences among many species in dewlap lepidosis provide several characters that are taxonomically useful. There are more or less distinct gorgetal and sternal scale-row arcs that differ interspecifically in number of rows, as well as in number, shape and size of the scales. There are small, closely set granular scales, here termed apicals, at the anterior and posterior corners of the dewlap. Anolis dewlaps are generally bordered by enlarged, imbricate marginals of a variable number of rows. Besides scalation, other interspecific differences occur in color, pattern and size of the dewlap. Where seasonally dry climates limit reproduction to a short and concentrated annual breeding season, dewlaps are usually relatively large and brightly colored. In relatively aseasonal climates of tropical rainforests and cloud forests, dewlaps are often relatively small and, whereas some are brightly colored, others are a dull brown, tan or white. These differences in dewlap size are significantly correlated with another variable that is linked to seasonality of environmentssexual size difference (males are larger than females in seasonal environments). In some instances, there also may be compensatory development of bright colors in small dewlaps or large size in those that are dull colored. MANY genera of iguanid lizards have conspicuous and distinctive organs, colorations or behaviors developed for visual display; the anole dewlap is one of the most specialized of these and is unique in various respects. Although characteristics of color and pattern of dewlaps have often been used in species descriptions of Anolis and are commonly used by many field-workers as means to identify species, most other morphological characteristics of dewlaps have received little study. Rand and Williams (1970) studied dewlap variability among eight sympatric species of Anolis at a single locality in Hispaniola, and considered the differentiation as it related to the premating isolation of the species. On the mainland of Middle America, however, considerably fewer species of Anolis are sympatric at most localities, and therefore the potential for interspecific competition and hybridization is greatly reduced. Our previous observations of Anolis in Middle and South America have suggested that interspecific variation in several morphological characters of dewlaps may be associated with seasonality of habitat. These observations prompted this study of the associations of lepidosis, color and size of dewlaps with environ