JESimpson, 1938. 90. 4700+ ft., La Sauceda, 15 mi. NNE. Cananea, Sonora. May 29, 1938, continued. Schuyler's ten rats for ten traps (but only 2 out of 7 in wooden rat-traps). The only difference between the setting technique in these two places was the lack of alpiste ('bird-seed') to mix with oat bait and 'chum' (ie. spreading some bait around trap). The lack of this additional bait may not account for the difference of 12 and 3 rats, but, I believe, it is probable a noteworthy factor. Señor Delgadillo caught five rats here in 17 traps using the last small bit of alpiste (some of which I took from the cheek-pouches of his specimens this morning); however, his catch at Santa Ana was small and at Bami (April 25, 1938) was zero; so I can not see but that the alpiste is a valuable asset for trapping D. spectabilis as it has been seen for other rodents here in Sonora this spring. Broke camp and drove 34.0 miles to Zorrilla, a railroad crossing and flag-stop for train and 6.2 mi. moré to Santa Cruz for meal. While eating we could hear and see partly the horse-race of the citizenry down the main-street. Drove 2.3 miles out of town to make camp at Rio Santa Cruz: 4650+ ft., 23 mi. S. Santa Cruz, Sonora. May 29, 1938, continued. Set out 41 mousetraps in river bottoms between cultivated fields and willow-brush also 50 live-traps between (and in) willow-brush and the river channel.