OF WASHINGTON. 261 
ter, occur in masses together, and this gregarious habit extends into the 
imago state. The flies are sluggish, and alight wherever they can find a 
suitable resting-place on grass or foliage, but, so far as I can learn, do no 
appreciable injury in any part of their existence, although some writers 
would have us believe that the larva? cause great destruction to the roots 
of grass. Bibio albipennis is probably the best known species in this coun- 
try, and owes its notoriety to its peculiar habits and to the fact that it is 
distributed over the greater part of the eastern half of the United States. 
It is found from Massachusetts to Colorado. Indeed, it might almost be 
said to extend from the Atlantic to the Pacific, for the species described by 
Loew as hirtus, which is found in California, is so near to albipennis that 
it is manifestly only a form of that species modified by a long residence on 
the Pacific slope. B.femoratus\s found from the Atlantic States to Michi- 
gan and Kansas, but does not seem to occur in such abundance as does the 
first-named species. 
The object of this paper is to bring to the notice of the Society several 
records of the fall occurrence of Bibionidce, to which my attention has 
been drawn more particularly by Prof. Lintner's notes on B. albipennis in 
his 2d New York Report, and to consider, in this regard, the question of 
their possible double-broodedness. 
I have gathered the following references to the literature on fall appear- 
ances of Bibio : 
1818. Meigen : Systematische Beschreib., etc., vol. i, pp. 310,317. 
1850. Zetterstedt: Diptera Scand., vol. ix, p. 3387. 
1856. Walker: Diptera Britann., vol. iii, pp. 137, 139. 
1869. Packard: Guide, etc., p. 392. 
1877. Siebke : Cat. Dipterorum Norvegiae, p. 188. 
1884. Williston: Stand. Nat. Hist., vol. ii, p. 412. 
1885. Lintner : 2d New York Report, pp. 114-115. 
Touching American species, we have statements by the following au- 
thors : 
Packard says that albipennis is "double-brooded and flies in swarms in 
June and October." He gives no details in this connection, but, replying 
to an inquiry, writes : "In regard to Bibio albipennis, I may say I have 
never reared the species, but must have made the statement in the Guide 
from seeing the swarms in June and September." 
Williston says virtually the same, stating that the flies of this species 
"are found in abundance on willows in early spring, but there is also 
another brood later in the season." 
In answer to a letter on this subject, Dr. Williston also wrote me : 
"It was impossible in my article to give credit for the different facts bor- 
rowed. I have observed Bibio albipennis among the earliest flies of spring, 
and again in October. I therefore gave the statement, which you will find 
in Packard's Guide, feeling sure that it was true. You will understand 
that the whole article is really a statement of our existing knowledge of 
