Crickson 1934 Thomomya b. chrysonotus. Ehrenburg, 288 ft. Yuma Co., Ariz. Feb. 20, 1934. Two individuals taken from seven settings made; five untouched. Settings made in gravel hills and sandy draw between them 3 mi. south of Ehrenburg and directly south of a broad wash. Specimen no. 389 taken from system of mounds near base of west side of coarse gravel ridge in sand with some small pebbles below surface. Creosote and Burrow weed commonest plants, a few small Palo verde trees and rat tail cactus near. Mounds about 100 yds. far and 25 ft. higher than willow association of Colorado River which comes directly to base of mesa at this point. Specimen no. 390 taken from system of mounds a mile free east of river bottom country on north east slope of ridge that rises directly from broad wash, surface soil coarse gravel cemented with sand, sand predominating below surface, only a few small bushes of creosote and burrow weed near. Mounds along two shallow draws; 33 in number, within an area of 15 sq. yds., mostly recently made and of large size, estimated 6-8 qts. of sand in each. Both males, testes enlarged. Made ten more settings in same general region; 1 in system from which no. 390 taken, and 6 in sandy draw about 100 yds. from bottom land, 3 in mounds within 25 yds. of place no. 389 secured. Ehrenburg, Feb. 21, 1934 Took 4 from setting near middle of sandy draw, and