79. Zuerfel 1953 Journal 2 mi. SW El Vezel (Yagunite) 7800', Chalchulma, Mexico July 2 Minimum temperature 48° F, maximum 77° F. The first heavy shower since we've been here in afternoon. Spend most of the morning putting up a bluebird and an oliv warbler which I shot. The rains stimulated the Cleatherodactylus to begin calling after nightfall. Bill and I went out and caught three (as so account). Included among the garter snakes caught by that Jerry Klots and brought in by the Mexicans were our first specimens of Thamnophis aguae megaloops. We now have four species of Thamnophis from this locality, the others being T. errane, T. cryptopais and T. suffipunctatus. The presence of the four species at the same local presents an interesting ecological problem. T. errane appears to be decidedly Terrestrial - we have found it several times in the forest far from water. T. sufi-punctatus at the other extreme has not been found by us more than a few inches from water. The other two species are presumably largely aquatic, though the only T. cryptopais which I collected was 200' from the stream.