DIPTERA. . os | 
the localities where they were born and developed. Experience indicates that once 
gorged with blood they die. The swarms dwindle in proportion as they are carried 
away or move from their breeding places. 
if Close investigation with the microscope has failed to reveal any eggs in the ovaries 
of the females composing these swarms, and if they deposit eggs at all it is before 
congregating to attack animals. 
a These singular facts invite speculation and theory, but it were unwise to indulge 
in these before we have learned more about the eggs, when and where deposited, and 
whether the females depositing them are in any way different from those comprising 
the swarms. Dr. Fritz Miiller has published in the Archivos do Museu Nacional do 
Rio de Janeiro, Vol. IV, page 47, Pls. I[V-VII,' some very interesting observations on 
another fly (Paltostoma torrentium), the larva of which is only found in the torrents 
y and cascades of certain streams descending the mountains of Brazil. There the 
pupz fasten by the flat venter to the rocks under water, and change into the per- 
fect flies. He found by opening the mature pupz that there are always two forms 
E of females associated with one form of male. The one form of female possesses a 
i rudimentary mouth, only fit to sip honey, while the other has a mouth well adapted 
to penetrate the skin of warm-blooded animals and to suck blood. 
The male Simulium, so far as known, is only found near where it developed. The 
structure of its mouth prevents it from biting, and it shows no inclination to join 
the roving swarms of females. Hence pairing of the sexes must take place in the 
vicinity of birth, and the eggs are probably deposited soon afterwards. It is also 
possible, as in the case of other Diptera, that the eggs are already well developed in 
the pupa. 
The condition of the inundated region forbids an indiscriminate selection of places 
to deposit in, since the young larve must in time find suitable swift currents of 
water after the subsidence to the normal level. Such breeding places we hope to be 
able to map out in future. 
It has also been claimed that a number of successive broods of the buffalo-gnat 
appear in early spring. If such were the case the relationship between the presence 
of the gnats and an overflow could be very readily imagined; but we have already 
shown that there is absolutely no proof thus far of more than one annual brood. 
Mr. Webster, while studying in the neighborhood of Vicksburg last spring, was 
impressed with the idea that the connection between the Simulinum increase and 
overflows was dependent upon the condition of the levees, in that the river water 
; in swelling the waters of the bayous not only creates a stronger current in the main 
bayou, but brings the current in contact with many trees and shrubs, as well as 
stumps and vines, along the bayous, thereby offering much greater chance for the 
larv to attach themselves. 
While we were at first inclined to give some weight to this view, and it seemed to 
afford an additional important argument in favor of keeping the levees in good con- 
dition, a survey of the whole field leads us to abandon this as the most important 
cause in the increase of the gnats during the period of the overflow, and to adopt 
the theory already advanced, viz., that the connection is at least partly due to the 
gnats being driven by the advancing waters from the lower to the higher lands. 
Another theory, not supplanting this last, but supplementing it, we would advance 
here: There is no doubt but that the advance of the waters from the main river and 
d their commingling with the clearer streams and tributaries carry asuddenly increased 
food supply, in the way of minute crustacea and other aqnatic creatures, to the 
Simulium larve just at the season when these are about to transform. It is quite 
probable that development in these larvze remains more or less latent or stationary 
during the cold winter months or when the water in which they occur is depleted of 
as 
me 
is 
5 
= 
s ' Reviews of his paper appeared in Kosmos, Vol. VIII, pp. 37-42; Nakire, July 7, 
J 1881, p. 214; Entomologist’s oe Magazine, February, 1881, p. 206 and pp. 
130-132, and March, 1881, pp. 225, 226. 
