Cope's Gray Treefrog

From Wiki: Cope's gray tree frog[2] (Hyla chrysoscelis, also called the southern gray tree frog) is a species of tree frog found in the United States. It is almost indistinguishable from the gray tree frog, Hyla versicolor, and shares much of its geographic range. Both species are variable in color, mottled gray to gray-green, resembling the bark of trees. These are tree frogs of woodland habitats, though they will sometimes travel into more open areas to reach a breeding pond. The only readily noticeable difference between the two species is the call — Cope's has a faster-paced and slightly higher-pitched call than H. versicolor. In addition, H. chrysoscelis is reported to be slightly smaller, more arboreal, and more tolerant of dry conditions than H. versicolor.
Both H. chrysoscelis and H. versicolor have bright-orange patches on their hind legs, which distinguishes them from other tree frogs, such as H. avivoca.[3] The bright-yellow pattern is normally hidden, but exposed when the frog leaps. This "flash pattern" likely serves to startle a predator as the frog makes its escape.[4] Similar hidden bright patterns are common in various Lepidoptera, for instance moths of the genus Catocala.[5] Both species of gray tree frogs are slightly sexually dimorphic. Males have black or gray throats in the breeding season, while the throats of the females are lighter.[6]

H. chrysoscelis male showing black throat
Microscopic inspection of the chromosomes of each species reveals H. versicolor has an extra set. H. chrysoscelis is diploid, having two complete sets of chromosomes, the usual condition in vertebrates. H. versicolor is tetraploid, having double the usual number of chromosomes. Generally, H. versicolor is believed to have evolved from H. chrysoscelis in the last major ice age, when areas of extremely low temperatures divided populations. Despite currently sharing habitat, the two species generally do not interbreed.