_Hyla phlebodes_ inhabits regions having rainfall throughout the year. Although large breeding congregations are most common in the early parts of the rainy season, males probably call throughout the year. At Puerto Viejo in Costa Rica the senior author has heard _Hyla phlebodes_ in February, April, June, July, and August. Charles W. Myers noted calling males of this species in the area around Almirante, Bocas del Toro Province, Panamá, in September, October, and February. An exception to the correlation between rainfall and breeding activity was noted by the junior author in _Hyla phlebodes_ in the Canal Zone, where he noticed a decrease in activity of that species in October and November, when the rains are heaviest and most frequent. Furthermore, independent observations made by both of us indicate that _H. phlebodes_ does not reach peaks of activity during or immediately after heavy rains, but instead builds up to peaks of activity two or three days after a heavy rain. This is in contrast to the other species, all of which characteristically inhabit drier environments than does _H. phlebodes_. Peaks of breeding activity in the other species occur immediately after, or even during, heavy rains. The calling location of the males generally is on vegetation above, or at the edge of, the water. _Hyla microcephala_ and _H. phlebodes_ call almost exclusively from grasses and sedges; _phlebodes_ usually calls from taller and more dense grasses than does _microcephala_. Except for some minor differences in calling location observed by the junior author (Fouquette, 1960b) in the Canal Zone, the differences in density and height of grasses utilized for calling-locations probably is dependent primarily on the nature of the available vegetation. Although bushes and broad-leafed herbs are usually present at the breeding sites, males of these species seldom utilize them for calling locations. Both _H. robertmertensi_ and _H. sartori_ have been observed calling from grasses, herbs, bushes, and low trees. Calling males of _robertmertensi_ have been found two meters above the ground in small trees. Daytime retreats in the breeding season sometimes are no more than shaded clumps of vegetation adjacent to a pond or in clumps of grass in a pond. Individuals of _H. m. underwoodi_ were found by day under the outer sheaths of banana plants next to a water-filled ditch. Dry season refuges are unknown. Amplexus is axillary in all four species. Egg deposition has been observed in _H. m. microcephala_, _m. underwoodi_, and _phlebodes_. In all three the eggs are deposited in small masses that float near the surface of the water and usually are at least partly attached to emergent vegetation. Each clutch does not represent the entire egg complement of the female.