48 INSECTS AFFECTING DOMESTIC ANIMALS. 
or later in the neighborhood of their breeding places. The number of 
individuals in a swarm can not be computed, as it varies greatly. The 
swarms lead a roving life, being drifted about by the wind and are 
frequently carried long distances from their usual haunts. 
At first the members composing a swarm are very active and bloodthirsty; but 
they soon die, and the swarm decreases gradually and soon disappears entirely. 
New swarms appear continually and replace the former ones. The duration of an 
invasion throughout the regions infested varies from a few days to five or six 
weeks. If cold weather follow their appearance, the gnats become semi-dormant; 
they are not killed by it nor by rain, but revive and become aggressive again with 
the first warm rays of the sun. Hot weather, however, soon kills them and puts an 
end to any further injury. The duration of life of a single individual is short; at 
least specimens confined even in large and well-lit boxes soon die. Buffalo-gnats 
that have once imbibed blood of any animal alsosoon die, as seen by the large num- 
bers found dried up in stables in which they have been carried attached to mules or 
horses. In the fields gnats filled to repletion with blood drop to the ground and 
crawl away, soon to die. They suffer, therefore, from their bloodthirsty habits, and 
this seems to be quite a general rule with all those blood-sucking species which are 
known to annoy man and other warm-blocded animals; for the love of blood gener- 
ally proves ruinous to those individuals which are anxious to indulge in it, as we 
have shown to be the case with the harvest mite or jigger. ' 
CHARACTER OF A SWARM. 
The number of individuals comprising a swarm can not be computed, as swarms 
vary greatly insize. Their presence is at once indicated by the actions of the various 
animals in the field. Horses and mules snort, switch their tails, stamp the ground, 
and show great restlessness and symptoms of fear. If not harnessed to plow and 
wagon they will try to escape byrunning away. Cattle rush wildly about in search 
of relief. Formerly, when deer were still numerous, they would be so tormented by 
these insects as to leave their hiding places and run away, seeking protection even 
in the presence of their greatest enemy, man. Approaching animals in the field, we 
notice at once small black bodies, exceedingly swift in their flight, darting about 
their victims in search of a suitable spot to draw blood. But even during a very 
general invasion by these gnats these insects are not uniformly distributed through- 
out the region infested, but they select certain places. Only low and moist ground 
is frequented by them; exposed or sunny spots are never visited. There may be no 
indications of gnats ina whole neighborhood, and the unprepared farmer, dreaming 
of no danger to his mules or horses in passing dense thickets of bushes, etc., near the 
roadside, is suddenly attacked by a swarm of these pests, and is frequently unable 
to reach a place of safety in time to save his cattle. As suddenly as such swarms 
appear, just as suddenly do they disappear. During a gnat season cautious farmers 
never travel with their horses or mules without providing themselves with some kind 
of protective grease. | 
When buffalo-gnats are very numerous the whole air in the vicinity of our domes- 
tic animals is filled with them at times, and looking toward the suffering brute, one 
sees it surrounded by a kind of haze formed by these flying insects. Sweeping rap- 
idly with the hand through the air one can collect hundreds of gnats by a single 
stroke. They crawl into everything, and the plowmanhas constantly to brush them 
away from his face, which does not always prevent them from entering and filling 
his mouth, nose, and ears; he is so tormented by them, and frequently by their bite 
as well, that he has to cease working for the time being. Thousands try to enter 
— 
'See American Naturalist, Vol. VII, 1873, p. 19. 
