a ear 
DIPTERA. Be 
small, will produce accelerated motion of the water. In the latter sudden bends are 
the chief cause. In the former there are numerous places where the larv# can 
securely fasten themselves, because large numbers of sticks partly embedded in the 
mud are not disturbed by the rising water. 
In many places the rocky beds of streams furnish excellent support 
for certain species. In such places as these they occur more or less in 
clusters, fastened by the posterior end of the body and capable of con- 
siderable movement, by traveling with a looping gait, by attaching 
themselves with silken threads and then allowing the current to move 
them about, or by floating free with the current until finding a satisfae- 
tory place in which to fasten again. 
The food of the larve has not been determined for many of the 
species, but the Southern buffalo gnat has been proven to be carniv- 
orous, and in all probability other species have a similar habit. 
The pupa of the species of Simulium is peculiar and distinguished 
from most other dipterous pup by the presence of a tuft of respira- 
tory filaments starting from each side of the thorax. (See figures of 
pup of Simulium pecuarum and meridionale.) These tufts are com- 
posed of a variable number of very slender filaments varying with the 
different species of Simulium. The abdomen is armed with spines, and 
at the tip are two larger bent spines or hooks by which the pupa anchors 
itself within the pouch-like cocoon. This cocoon is open at the upper 
end and allows the exposed head portion of the pupa bearing the 
respiratory filaments to have free access to the water. It is composed 
of silken threads, generally grayish in color, and is attached firmly to 
sticks, leaves, logs, or other objects in the current of water. 
Remaining but avery short time in the pupal state, prolonged or shortened by 
atmospheric influences, they give forth the winged insects. The length of the pupal 
state in the case of the turkey-gnat averages five days. Both larval and pupal skins 
remain for some time in the empty pouch. 
The perfect insects issue from their pupx under water, and surrounded, accord- 
ing to some writers, by a bubble of air. The silky hairs of the fly, however, are 
protection enough to prevent it from drowning. The winged insect pops to tbe 
surface like a cork, runs a few inches over the water, and darts away with great 
swiftness. 
The imago.—The perfect flies vary in length, the females being usnally the larger. ° 
They are characterized by their peculiar short and thick shape. The head is bent 
under, and is nearly as wide as the very large and humped thorax. The thick 
antenne are composed of twelve stout joints; the four-jointed palpi terminate in 
long and fine joints; the posterior shanks and the first joint of the hind tarsi are 
somewhat dilated. The free labrum is as sharp as a dagger, and the very prominent 
proboscis is well adapted for drawing blood. The insects possess no ocelli, but their 
eyes are large; in the male they join at the forehead, but in the female they are far- 
ther apart. The mouth organs of the male are also not so well developed as in the 
female, being soft and unable to draw blood. The bodies of these gnats are quite 
hard and can resist considerable pressure. * * * 
The gnats are exceedingly active, and endowed with very acute senses, which enable 
them to find unerringly animals a long distance away. Only females seem to form 
these aggressive swarms, since not a single male has been found in the large num- 
bers captured and investigated. The male stays near the place of its birth, and since 
