Tehuantepec - Oaxaca Highway. May 4 Km. 153 - collected 2 C. humilis and heard several others singing = 10 km. from Tequisistlan (=SE). Then drove on to within 5 mi of Tequisistlan, 1000 ft. +-, and made camp just off the road in a cactus-deciduous tree forest where we found worms almost as common as in the Tehuantepec lowlands. Photographs Roll #23 (color) 1x2 show place where we watched a pair of C. humilis foraging. Later I found several other pairs more or less evenly spaced in this vegetation stand and collected two additional specimens. May 5 Collected 4 more specimens and then headed north to Oaxaca. Camped 16 mi. along road from camp we reached the upper limit of the forest and entered grassy hills spotted with pines. 16 miles more (at Rio Hondo) we hit C. humilis vegetation again. 18 miles beyond at K-690 we entered pine oak forest - open type and 2 miles beyond we took a picture (#3) of El Camaron Valley, at El Camaron worms (C. humilis) singing commonly in guanuche and other riparian vegetation similar to riparian in Tehuantepec region. A good minosa-cactus formation on slopes but only up the slopes a short distance it is pine forest. Took photo looking up the river where we heard humilis singing commonly. May 5-1 A short way up the slope from the river I found a pair with a nest (plant collected) in a broad-leaved tree. Also collected one other common tree. The nest seemed about