12s Myron Harmon Swenk 
19. Lobes of the seventh ventral plate hairy from lateral bristle tufts 
£G tapess: WO mt. Weis Ras), sam eines ie cited Rete eee fulgidus 
19. Lobes of the seventh ventral plate glabrous on most of the striated 
Miskin ats ee oS wi els ROR ee alalce SRR ee ne aver a 
20. Lobes of seventh ventral plate roughly trapezoidal; 10 
AMATI. 2 oc Ne eg hence oh eeieken cto o erotik aieth ber emcee te anes nevadensis 
20. Lobes of seventh ventral plate columnar, expanded abruptly 
into lateral prolongations apically; 8-10 mm.......... armatus 
(The males of chamaesarachae, crawfordi, banksi, texanus and tegularis 
are not known.) 
Colletes brevicornis Robertson. 
1897. Colletes brevicornis Robertson, Transactions of the Academy of 
Science of St. Louis, vii, pp. 315-16, 3 (May 7, 1897) ; original 
description. 
1900. Colletes brevicornis Robertson, [bid., x, p. 51, 2 (February 21, 
1900) ; description of female. 
1904. Colletes brevicornis Robertson, Canadian Entomologist, xxxvi, no. 
9, p. 275, 2, p. 276, d (September, 1904); in table of Illinois 
species. 
1906. Colletes brevicornis Robertson, Science, xxiii, p. 309 (February, 
1906) ; season, food plant. 
1906. Colletes opuntiae Cockerell, Annals and Magazine of Natural His- 
tory, series 7, xvii, pp. 312-13, ¢ 2 (March, 1906); original 
description. 
1907. Colletes brevicornis, form opuntiae Cockerell, University of Colo- 
rado Studies, iv, p. 240, do & (June, Oe in table of species 
of Boulder county, Colorado. 
9. Length 9-10 mm. Eye orbits rather strongly converging below. 
Clypeus strongly convex, punctured closely and evenly with rather large, 
round punctures, nowhere distinctly striate, its pubescence scattered, short 
and pale. Supraclypeal area convex and punctured like clypeus. Front 
coarsely and closely punctured and clothed with short, erect, grayish white 
pubescence. Cheeks finely and indistinctly punctured, the orbits bounded 
by an impunctate line, the pubescence sparse and white. Mandible and eye 
all but touching, the length of the malar space less than one-eighth its 
width. Antennae short, heavy, clavate, joint 3=4-+5, the proportion being 
5:3:2, joints 6 and 7 as long as wide, following joints only three-fourths 
as long as wide. Flagellum paler below, dusky to brownish. Vertex shin- 
ing, coarsely but separately double punctured, a few of its long hairs black 
but most of them pale. Prothoracic spine a mere blunt angulation. Meso- 
thorax shining, the punctures large, round, and deep, everywhere well- 
separated, especially on the disk. Scutellum similarly but rather more 
coarsely punctured. Postscutellum with punctures small, separated me- 
54 
