16 Myron Harmon Swenk 
punctured, especially the apical ones, segments 1-5 with narrow white apical 
fasciae continued indistinctly on venter, the basal truncation subimpunctate 
and with short, rather dense, erect white hairs around its margin, the rest 
of tergum with short scattered hairs becoming.longer and denser apically, 
largely dark on segments 3-6. Segments distinctly depressed on apical 
margin of 1 and base and apex of 2. 
3d. Length 9-10 mm. Differs from the 2 as follows: Pubescence longer, 
the black thoracic hairs almost wanting; clypeus more pubescent, its me- 
dian sulcus generally lacking; vertex less depressed and entirely punc- 
tured; antennae nearly concolorous, joint 3 shorter than 4 or 5, the pro- 
portion being 4:5:5, the median flagellar joints not longer than broad; 
prothoracic spine shorter; malar space about one-half as long as broad; 
anterior femora with a few long hairs; basal joint of hind tarsi three 
times as long as broad, middle joints one and one-half times as long as 
broad. 
Genitalia.—Stipes notched, its apex poorly defined, very small; sagittal 
rods parallel and expanded apically into subtriangular lobes; volsella very 
large, over one-half as long as sagitta; seventh ventral plate small, largely 
membranous, thinly haired except on margins where it is glabrous, ex- 
ternally with a blunt lateral lobe-like prolongation probably representing 
the external costa. (Plate 1, figures 2 and 2a.) 
Type Locatiry.—Carlinville, Illinois; types in collection of 
Mr. Charles Robertson. 
The unique puncturation of the clypeus is the best character 
for readily recognizing either sex of this species. C. willistom 
is allied, though not closely, to C. latitarsis, and has remarkably 
similar habits. Mr. Robertson gives its season in Illinois as May 
28 to September 5, and points out that it visits Physalis with 
latitarsis, but does not enjoy so long a season, which is also an 
earlier one, and is not so common as Jatitarsis. In Nebraska, 
willistoni flies from the last few days in May to the first of Sep- 
tember, being commonest from late July to late in August, and 
I have captured it along with /atitarsis on Symphoricarpos and 
Melilotus during late June and early July, but it seems to disap- 
pear before the goldenrod flourishes and is by far the most com- 
mon at flowers of Physalis. In Texas it begins to fly in early 
April. Its range is a broad one, from the Atlantic coast (Wash- 
ington, D. C.) west to Sioux county, Nebraska, and south to cen- 
tral Texas (Fedor), but it is apparently not an abundant species 
anywhere. 
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