Adult: Species description based on Savage (2002). A very small species. Males to 26 mm, females to 30 mm. Dorsal: Dorsal coloration light brown with extensive markings, including 1) dorsolateral or middorsal stripes, a light patch between the shoulder blades, and a dark bar between the eyes. The legs are also barred. The dorsal surface is warty with a small amount of ridging. Ventral: The ventral surface is yellow, with dark mottling on the throat. Concealed surfaces: The rear surface of the thigh and groin are reddish brown; some red coloration may extend onto the upper surface of the thigh. Extremities: Feet without webs.
Habitat: Premontane and lower montane forest between 920 and 1590 m. Ecology: Craugastor underwoodi is diurnal and lives in leaf litter (Savage 2002). Call: A squeak, squeak (Savage 2002). Karyotype: 2N = 18 (DeWeese 1976, Savage 2002)
Diagnostic description: Tiny to small (males 16-26 mm, females from 18.4 to 30 mm) size; dorsum uniform brown to mottled light brown, or rarely with longitudinal dorsolateral or mediodorsal clear, granular or warts lines; dull yellow belly; yellow throat and breast, often mottled with dark pigment; with dark bars on the upper lip; belly with halos; surface of thighs reddish brown with dark bars (Savage 2002).
Habitat: Among forest litter (Savage 2002).
Reproduction: Produce encapsulated eggs, which are laid in terrestrial conditions; development is direct (no tadpoles) (Savage 2002).
Feeding: It probably feeds on small insects and spiders.
Behavior: Day (Savage 2002).
Distribution in Costa Rica: In the middle lands of the Cordilleras Tilarán Central Volcanic and Talamanca, 920-1600 m elevation (Savage 2002).