REPORT OF THE ENTOMOLOGIST. 509 



the inside of the open pouch. Remaining but a very 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 

 pujDal skins remain for some time in the empty pouch. 



The perfect insects issue from their pupee under water, and sur- 

 rounded, according to some writers, by a bubble of air. The silky 

 hairs of the fly, however, are protection enough to prevent it from 

 droAvning. The winged insect pops to the surface like a cork, runs a 

 few inches over the water, and darts away with great swiftness. 



The Imago. — The perfect fly varies in length from 3™™ to 4.5""", the 

 females being usually the larger; the Turkey Gnat is somewhat 

 smaller. Both insects are, like all other species of Simulium, char- 

 acterized 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 antennae 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 farther 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 color of the Southern Buffalo Gnat is 

 black, but covered with grayish-brown, short, and silken hairs, which 

 are arranged upon the thorax in such a manner as to show three 

 parallel longitudinal black stripes; the abdomen is more densely 

 covered with similar hairs, and shows, furthermore, a dorsal broad, 

 whitish stripe, which widens towards the posterior end. The legs 

 are more reddish, but also covered with hairs of the same color as 

 elsewhere; the balancers are yellowish-white and the wings ample. 

 The general appearance of the Turkey Gnat is very similar, but it is 

 lighter in color. 



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 numbers captured and 

 investigated. The male stays near the place of its birth, and since 

 females once gorged with blood do not and cannot return, copulation 

 and the depositing of eggs must take place very soon after emerging 

 from the water. These points have as yet to be investigated. 



NUMBER OF BROODS. 



All species of the genus Simulium, the life-histories of which have 

 been studied, are single-brooded, and no doubt Buffalo and Turkey 

 Gnats form no exception to that rule. Extending as they do over 

 such a vast area, we should expect their swarms in some seasons to 

 form and appear continuously for five or six weeks before the whole 

 brood had matured and disappeared. No Buffalo Gnats have ever 

 been found in the infested region during the summer, fall, or winter, 

 even when inundations have occurred in these seasons, and there are 

 no indications of a second or third brood in the same year. 



