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Glass frogs make up the family Centrolenidae, which consists of certain frog species that are known for being transparent or translucent. They reside in the tropical regions of Central and South America and are largely arboreal, living above the ground in trees and other vegetation.
The distinguishing feature of glass frogs is their transparency. While the skin of most species is not transparent on every side or appendage, each glass frog has at least a mildly transparent underside. When viewed from beneath, many glass frogs' organs such as the heart, gastrointestinal tract, and, on rare occasions, the lungs are visible. In some species the entire epidermal layer can be translucent.
The remainder of the frog's skin is predominantly green and usually spotted with blue, yellow, or black and white dots. Glass frogs average between .75 inches (3 cm) and three inches (7.6 cm) long, but several species of the Centrolene genus are much larger than the others and are even denoted as "giant" in some cases.
Most glass frogs are nocturnal, gathering much of their food and conducting most of their activities after the sun has begun to set. They do not spend much of their time on the ground. Instead, glass frogs usually reside amongst the vegetation and trees and are designated as arboreal or live near and in water and streams and are classified as riparian.
Glass frog species are largely found in fog forests. These forests possess an overabundance of vegetation and moisture, deriving their name from the low cloud cover around and often permeating the canopy, which is the highest level of vegetation. Fog forests are montane and appear just below the subalpine zone, the last level of vegetation before the tree line ends at a high altitude.
The fog forests that glass frogs tend to inhabit can be found between the southernmost tip of Mexico and Venezuela and Bolivia. While these forests provide an ideal environment that is rich with moisture and food sources, some glass frogs live outside these areas in the Tumbes-Choco-Magdalena, located along the Pacific coast of South America from Ecuador through Columbia and Panama. Other glass frogs reside in parts of the Amazon rainforest as well as a few other locations in South America that extend as far south as Argentina.
Mating, for most glass frogs, takes place along streams. Males produce a mating call to attract a female. When a nearby female glass frog responds, mating commences, and the eggs are laid on vegetation hanging over the stream. The eggs or larvae that develop fall into the stream when pushed by the rain.