A recently metamorphosed young has a snout-vent length of 15 mm.; the head is as long as wide, the eyes are prominent; the limbs are weakly barred; the skin is rugose above and granular below. The venter is immaculate; the dorsum and limbs are gray-brown in preservative (pale green in life). The interorbital space, supratympanic fold, and scapular region are darker than the rest of the body; the fingers lack webbing; the webbing on the foot is the same as in adults; small metatarsal tubercles are present, but the tarsal fold is absent.
[Illustration: Fig. 2. Tadpoles of (A) _Hyla boulengeri_ (KU 104295) and (B) _Hyla elaeochroa_ (KU 104134), × 3.]
[Illustration: Fig. 3. Mouthparts of tadpoles of (A) _Hyla boulengeri_ (KU 104295) and (B) _Hyla elaeochroa_ (KU 104134), × 25.]
_Remarks._--Cope (1887:12) described _Scytopis boulengeri_ from Nicaragua. Günther (1901:267) placed _boulengeri_ in the genus _Hyla_, and stated that Cope possibly placed _boulengeri_ in the genus _Scytopis_ on the supposition that it had an accumulation of "sebaceous glands" above the tympanum. Noble (1918:339) redescribed _Hyla boulengeri_ on the basis of three specimens from Zelaya Province, Nicaragua, and noted that the glands were not prominent in any of the specimens. Duellman (1956:8) showed that _Scytopis hebes_ (generotype of _Scytopis_ by monotypy) is a Phrynohyas, and thus placed _Scytopis_ Cope, 1862, in the synonymy of _Phrynohyas_ Fitzinger, 1843.
Dunn and Emlen (1932:25) placed _Hyla lancasteri_ Barbour in the synonymy of _Hyla boulengeri_; the former was known solely from one juvenile. They made no qualifying statements, but probably they were impressed by the strongly barred thighs, a coloration known among Central American hylids at that time only in _Hyla boulengeri_ (Duellman, 1966a:271). Taylor (1952:856) followed Dunn and Emlen with reservation and noted some differences. Duellman (1966a:271) showed that the holotype of _lancasteri_ was a juvenile of a species subsequently named as _Hyla moraviaensis_ by Taylor (1952:865).
In Central America, _Hyla boulengeri_ can be confused only with _Hyla foliamorta;_ the latter is restricted to central and eastern Panamá and northern Colombia. The snout of _foliamorta_ is more pointed and protruding, and the vocal sac is darker than in _boulengeri_; the groin of _foliamorta_ usually is creamy white, whereas _boulengeri_ usually has a dark spot. The skulls differ in that _boulengeri_ has a frontoparietal fontanelle, the prevomer is larger and elongate, anteriorly connected to the premaxillary, and posteriorly separated from the sphenethmoid by cartilage; _foliamorta_ lacks a fontanelle, the prevomer is smaller, anteriorly separated from the premaxillary by cartilage, but connected by a bony suture to the sphenethmoid. The mating call of _boulengeri_ differs by having shorter notes, twice as many pulses per second, a higher fundamental frequency, and more closely approximated major frequencies than does that of _foliamorta_.