Illinois is home to 10 species of the Hylidae family of frogs. Frogs from this family are what is known as New World tree frogs. Consisting of more than 700 species, most members of this family have large finger pads on their feet which act like suction cups to help the frogs climb trees.
Northern Cricket Frog
The northern cricket frog grows to just over an inch in length. It has an olive-brown color with a green or red stripe along its back. The frog is found throughout the state.
Bird-Voiced Tree Frog
The bird-voiced tree frog grows to just over an inch in length. It has a gray-brown to greenish coloring with a darker cross or star-shaped marking on its back. The species is found in the most extreme southern counties of Illinois.
Green Tree Frog
The green tree frog grows to just over 2 inches in length. It has a bright green to yellowish color with paler stripes on its sides and the corner of its mouth. The frog is found mostly in the southern counties.
Gray Tree Frogs
In the state, three species of grey tree frogs are found which are physically identical to one another. Cope's grey, grey complex and the eastern grey are all just over an inch long with brown to greenish-brown coloring and a darker brown cross-shaped marking on their backs. The species can only be identified by DNA testing. All three species are found throughout the state.
The spring peeper grows to just over an inch in length. It is tan to gray-brown in color with a darker, X-shaped pattern on its back. The frog is found mainly in the eastern and southern counties of the state.
Southeastern Chorus Frog
The southeastern chorus frog grows to 1 1/2 inches in length. It is a tan to gray-brown colored frog with darker spots and stripes running along its body. The frog is found in the most southern counties of the state.
Strecker's Chorus Frog
Strecker's chorus frog grows to just under 2 inches in length. It's a gray-brown colored frog with dark-brown to black-mottled stripes along its body. It lives in just a few counties in the west and south of Illinois.
Western Chorus Frog
The western chorus frog grows to 1 1/2 inches in length. It is tan to grayish-brown in color with darker mottled stripes running the length of its body. It lives throughout most of the state and is a common species.