144 KANSAS UNIVERSITY QUARTERLY. 
The specimen, from which the description is drawn, was captured 
on flowers of Rubus May 18, 1895. Of the other two, one was 
captured May 23, 1896, the other May 16, 1897; the former ‘has 
the brown color of wings more even throughout; on each side of 
the second abdominal segment at base between the lateral yellow 
spot and the black dorsal middle the color is dark reddish brown; 
the latter with the impression of the face more conspicuous; both 
are more robust, first joint of antenna blackened at the extreme 
apex only, scutellum with disk yellow, not reddish or brownish 
(the yellow ground color may change after death to yellowish or 
reddish brown); all three specimens belong, however, to the same 
species. 
To Certa Williston’, n. sp. I refer Certa signifera described by 
Williston in his Synopsis of N. Amer. Syrphide, 1886, p. 262. 
Williston writes: ‘‘One male specimen from Professor Riley’s col- 
lection (Florida), and three females in the Loew type collection 
from Texas (Boll), bearing the label ‘signifera?’ in Loew’s writ- 
ing. I find discrepancies in the original description which make 
me doubt that this determination is the correct one.” The speci- 
mens from Texas, included under C. signifera Loew in the Catal. 
N. Amer. Diptera, 1878, p. 139, by Osten Sacken, are also referred 
to C. Willistoni n. sp., as being the same ones that Professor Wil- 
liston examined in the Loew type collection of the Mus. Comp. 
Zool., Cambridge, Mass. 
Giglio-Tos (Ditteri del Messico, I, p. 32; 1892) writes about the 
single female (C. signifera Loew) before him: ‘‘L’esemplare 
femmina, che ho esaminato, corrisponde bene alle. descrizioni 
minute del Loew e del Williston.” Giglio-Tos was not aware, 
however, of the differences in the respective descriptions of those 
dipterologists regarding the antennal joints; whether or not his 
female from Cordova (Mexico) is the C. s¢enifera Loew has still to 
be ascertained. 
Professor Johnson in his list ‘* Diptera of Florida” (in the Proc. 
Acad. Nat. Sc., Philadelphia, 1895,) records ‘‘ Ceria signitfera 
Loew, Inverness, February 12, 14 (Robertson),” but as his record 
is not accompanied by other notes, it may be doubtful whether 
his specimens belong to Loew’s signizfera. The occurrence of C. 
signifera Loew in the U. S. has yet to be confirmed. 
Ceria signifera Loew (Neue Beitrige I, p. 18, 19; 1853,) and 
Ceria Willistoni n. sp. differ essentially as follows: 
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