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5O INSECTS AFFECTING DOMESTIC ANIMALS. 
many localities entirely dependent upon these streams for their water supply, and 
the introduction of poisonous substances might cause much trouble. 
Some of the experiments were made by confining the larve in glass tubes and 
submitting them to a current of water to which the following decoctions and solu- 
tions had been added, viz: China berries, salt, lime, sulphur, tar water, kerosene 
emulsion, and carbon-bisulphide. Strong tar water killed them; diluted, it proved 
harmless. Kerosene emulsion diluted to contain 5 per cent kerosene was effective; 
3 ounces of carbon-bisulphide in 7 quarts of water proved fatal within ten minutes; 
the other insecticides were ineffective. It would be very costly to put enough of 
these materials in the water to produce the desired effect. 
If the general opinion that broken levees are to blame for the destructive swarms 
of buffalo-gnats prove to be the correct one, the restoration of such levees would, 
within a few years at most, restore the former immunity from these insects. This 
time would be materially hastened by the removal of obstructions in all such parts 
of the bayous where they would come 1n contact with the swiftest current. 
OVERFLOWS AND BUFFALO GNATS. 
It is very generally claimed by the inhabitants of the infested region that as long 
as the States bordering upon the Mississippi River had a perfect levee system, which 
prevented the water from escaping into the inland bayous, no damage was occa- 
sioned by buffalo-gnats, not even in districts now badly infested. It is further 
claimed that the buffalo-gnats appear with every overflow, and only with an over- 
flow if such overflow occur at the proper season and with the proper temperature, 
viz., during the first continuous warm days of March, April, or May. 
The chronological data already given seem to prove such assertions correct. Too 
much weight should not, however, be attached to these data. The region is as yet 
rather thinly settled, and no systematic records of the appearance of buffalo-gnats 
in injurious numbers have ever been kept. A general and widespread appearance of 
these insects seems to take place, however, only during an inundation, and, granting 
the connection between the two phenomena, the causes for it are yet obscure. It 
was by the elucidation of this problem that we hoped to discover some means of 
preventing the injury of the flies by preventing the multiplication of the larvx. 
Inundations in the lower Mississippi Valley are not occasioned by local rains, but 
by the immense volume of water brought down by the river and its more northern. 
tributaries, and such overflows first take place in the northern regions infested by 
the buffalo-gnats, and not in the southern. The earlier appearance of these insects 
in the South would seem to invalidate the prevailing belief that an overflow brings 
them. Similar conditions prevail in Hungary, where a closely allied insect does so 
much injury to all kinds of live stock. There the gnats appear every spring in 
varying numbers, forming local swarms which move about with the wind; but no 
general invasion takes place until the River Danube inundates the region infested. 
Is it not probable that swarms of these gnats are forced by the conditions conse- 
quent upon an inundation to extend their flight beyond their usual haunts to the 
more elevated and drier regions, and that in this fact we have at least one of the 
causes of the connection? Small swarms, otherwise local and unobserved, would 
thus, during a period of high water, be forced to band together in such immense 
armies. There must be other reasons, not yet clearly demonstrated, why these 
insects appear in such vast swarms with an overflow, and this problem can only be 
solved by a critical study of many breeding places during several seasons over the 
whole region involved. 
Some peculiarities of the swarms of buftalo-gnats have been observed, and these 
may, by closer study in future, throw some light upon the problem. It is to be 
noted that all the specimens composing these swarms are females, and that not one 
male has been found among them either here or in Europe. There is every reason 
to believe that none of the females composing the blood-thirsty swarms return to 
—— Be er a pe oe ee 
