(A) A breeding pond (approximately a 1 x 1 m area; water temperature of 5.9 C; 120 m elevation), having 26 pairs of egg sacs of H. nigrescens and five pairs of egg sacs of H. lichenatus, located at Yamanome, Ichinoseki-shi, Iwate Prefecture, Japan (21 April 1984). At this time, snow covered some places around the pond.

(B) A cooler box with water, including five males of H. nigrescens (large ones) and five males of H. lichenatus (small ones), collected from the pond. Mean snout-vent length (SVL: distance from the tip of the snout to the posterior angle of the vent) of the former was 81.56 mm (SD = 2.29, n = 5, range 77.9-83.8), and that of the latter was 61.56 mm (SD = 4.73, n = 5, range 56.8-69.4). There was no overlap between SVLs of these two species.

In a mixed oviposition of H. nigrescens and H. lichenatus, we can distinguish these two species by referring to body sizes, even if they do not show any distinct aquatic-phase morphology.