Specific Characters in the Bee Genus Colletes 15 
1895. Colletes willistonii Robertson, Ibid., xxii, p. 116, ¢ (May, 1895) ; 
description of male. 
1904. Colletes Willistonit Robertson, Canadian Entomologist, xxxvi, no. 
9, p. 275, 2, p. 276-77, d (September, 1904); in table of Illinois 
species. 
1906. Colletes willistonti Robertson, Science, xxiii, p. 309 (February, 
1906) ; season, food plant. 
?. Length 8-11 mm. Orbits moderately converging. Clypeus with 
sparse, shallow, quite weak punctures on a dull, minutely striate, rough- 
ened surface, the median sulcus weakly defined or not at all evident, no 
indication of striae, and clothed with a few short, pale hairs. Supra- 
clypeal area sculptured like clypeus, wholly punctured and opaque. Face 
with close, strong, deep punctures and short, whitish pubescence. Vertex 
strongly double punctured, almost bare but with a. few long, pale hairs 
and no black ones in interocellular space, the foveae extending back to 
form a depression, the occiput fringed with short, dense, white pubescence. 
Cheeks weakly and sparsely punctured, with a few white hairs near man- 
dibles, occiput with a fringe of short, dense, white hair. Malar space short, 
about one-sixth as long as broad. Antennae black with the flagellum 
lighter beneath, sometimes bright brownish, joint 3 longer than 4 or 5, the 
proportion being 4:3:3, the median flagellar joints distinctly shorter than 
wide, scape punctured. Prothoracic spine slender and sharp, but so short 
as to be concealed by the pubescence. Mesothorax with large, coarse, 
moderately close punctures, widely separated on the small shining disk, 
sparsely clothed with short white hairs mixed more or less with dark ones 
on the disk. Scutellum with very large, coarse, shallow punctures, dense 
behind but fewer anteriorly, bounded behind by a fringe of dark and then 
another of pale hairs. Postscutellum finely roughened, its pubescence long 
and white. Base of metathorax with an angulation defining the superior 
face, which has a distinct series of pits which are shining and twice as 
long as broad, often squarish medially. Enclosure subtriangular, shining, 
the neck only one and one-half times as long as broad at base. Lateral 
faces of metathorax very slightly shiny, with sparse, weak punctures, and 
covered with long, white pubescence. -Mesopleura crowded with coarse 
but shallow punctures, their pubescence sparse, moderately long; white. 
Tegulae shiny black. Wings hyaline, nervures dark testaceous to blackish, 
stigma rufo-testaceous. Legs stout, black, covered with whitish pubescence 
nowhere mixed with black hairs, longest on anterior femora and posterior 
tibiae, the inner tarsal apices golden-tufted. Basal joint of hind tarsi be- 
tween two and one-half and three times as long as broad, middle joints 
one and one-half times as long as broad. Claws dark red with a short 
median tooth. Tibial spurs dark testaceous, the hind one of hind tibiae 
finely ciliate. Anterior coxae feebly spined. Abdomen stout, subconical, 
slightly shiny, closely and finely punctured, the first two segments strongly 
so, closer and finer on the second, the following segments finely and feebly 
a7 
