Nov. 6 Casita, 40 km. S Nogales, 992 m, Sonora. Camp is located on the ranch of Guirivaldo Eldias, just west of the Southern Pacific tracks on a valley flat over which there are scattered small swampy spots, surrounded by small fields now covered with dry weeds, and over the valley flat are scattered rows and groves of large willows and, in local areas, a species of walnut or butternut. On the higher parts of the flat, along its periphery, are occasional, large live oaks. Near camp there are fenced-in, cultivated fields, and the remainder of the valley is grazed. Peripherally, also, there are mes- quite groves that extend up onto the hills. The valley bottom represents one major habitat; the other is the upland woodland of oaks. The mesquite mentioned above ext- ends upward onto the lower hills, and then becomes less and less frequent to the crest of the low mountain range just west of camp. Along the crest, mesquite occurs apparently chiefly where grazing has elimi- nated most other vegetation. The woodland consists in most part of two species of oak, one suggestive of our Q. douglasii, the other of our Q. wislizenii. The first occurs on both drained slopes and in the arroyos; the second occurs along the arroyos and on the immediately adjoining slopes.