determined by a simple dominant gene in Rana limnocharis, Rana ridibunda, Rana sylvatica and Rana arvalis; that means the individuals both homozygtes by allele determining the presence of stripe and heterozygotes have the stripe, whereas only the individuals homozygotic by recessive allele are non-striped. The proportions of striped specimens in populations of some frogs show clinal variations. For example, the proportion of striped Rana sylvatica in North America generally increases towards the west and north. The variations in the proportion of different color may relate to either genetic-stochastic processes. or their adaptive importance. For different colour morphs of Acris crepitans, the hypothesis about the direct adaptive value of different colour morphs (for escaping predation) competes with the hypothesis that these morphs correlate with thermotolerance. Striped specimens Rana sylvatica, striped specimens better perform in open areas. Differences in the proportion of striped frogs in Rana arvalis are explained with physiological differences between the morphs. Striped recently metamorphosed frogs have a relatively large liver, in comparison with unstriped ones, and their weight increases more rapidly. Tadpoles of striped Rana arvalis need more time for completing metamorphosis but, after metamorphosis, their growth is faster than that of unstriped froglets. In a frog widespread in Turkey and the Caucasus, Rana macrocnemis, the proportion of frogs with the stripe increases with the altitude in mountains of the Lesser Caucasus, but not in the Greater Caucasus. Given the same altitude, non-striped frogs from the Greater Caucasus grow slower and maturate later than the striped frogs from the Lesser Caucasus, which provides them selective advantage in high mountains, but their tadpoles are likely to be less resistant to overheating than those of the non-striped frogs.