glass frog, (family Centrolenidae), any of a group of treefrogs found in the New World tropics, somespecies of which havetranslucent bellies and chests. In glass frogs the viscera are visible, and an observer can see theheart pumpingblood into thearteries and food moving through the gut. The translucency, which may also extend to thefrog’s sides and parts of its back, is a type ofcamouflage in which the edges of the frog blend with the relative brightness or darkness of its surroundings. This phenomenon, callededge diffusion, softens the line separating the colour of the frog’s skin from the colour of the background. Not all species have a translucent underside. Viewed from above, most glass frogs appear light green. Their patterning ranges from uniform green to green with white to yellow spots that mimic glass frogeggs. Glass frogs have expanded digit tips that aid in climbing, and thistrait allows most to live intrees orshrubs alongforest streams.

Glass frogs are classified in approximately 160species and 12genera (with most species classified in thegeneraCentrolene,Cochranella, andHyalinobatrachium). They occur fromtropical lowland forests to mid-elevationmountain forests. Most species are small, with adults ranging from 20 to 30 mm (0.8 to 1.2 inches) in total length. In a few species adults are larger, attaining a maximum length of nearly 80 mm (3 inches).

For mating to occur, males must first call to females. Calling males sit onleaves—either the top or underside depending upon the species—over streams orlake edges. When a female comes, she does not descend to the water with the male. Instead, they mate on theleaf with the male clasped to her back with his arms wrapped around her waist (a physical position calledamplexus). She deposits hereggs on the leaf, and, after she departs, the male often remains to protect the eggs from predators and to call additional females. Some males will attract other females and thus have several egg clutches in various developmental stages to guard. When thetadpoles hatch, they fall into thewater below. Tadpoles usually live and feed amid the leaflitter and streamsidedetritus until theymetamorphose into froglets. Among the major egg predators are “frog flies,” which lay their eggs on the egg masses. Theflies’ eggs hatch quickly, and the maggots feed on the frogembryos.

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