510 REPORT OF THE COMMISSIONER OF AGRICULTURE, 

 ENEMIES OF THE BUFFALO GNAT. 



The Buffalo Gnats in tlieir winged form have but few enemies? 

 among birds, because they usually a^jpear at a time in the early spring- 

 when but few of our insectivorous birds have returned from their 

 southward migrations. Besides the Mocking-bird and the Winter 

 Wren, birds which remain in the more southern portions of the in- 

 fested regions, no other birds have been observed to catch and feed 

 upon them. Hens and chickens eat large numbers of such gnats as 

 have become helpless by being gorged with blood. A single prema- 

 ture Dragon-fly, or Mosquito Hawk, and a brightly colored Hawk-fly 

 (Asilidce) were observed by Mr. Lugger to catch them in the fields. 

 But the larvse of the gnats do not fare so well. Although somewhat 

 protected by their color and position in the water, many are discov- 

 ered by small fishes belonging to the family Cyprinidce, which 

 frequent even the smallest creeks, and greedily eat them; other 

 fishes in the larger creeks will probably act in the same way. The 

 carnivorous larvae of Water-beetles, as well as other aquatic insects, 

 no doubt find them as well suited to their taste. The jjupse escape 

 detection much better, because they do not move, and are, as a rule, 

 hidden by the fine floating mud of the water which partially covers 

 them and their pouches. 



No insect enemies of any of the Simulnim larvae have been here- 

 tofore observed either in this country or in Europe. It is therefore 

 interesting to note that the larva of a si3ecies of the neuropterous 

 genus Hydrojosyche, has been found by Mr. Howard near Washing- 

 ton feeding upon the larvse of a local species of Simulium. The 

 facts were communicated by him to the Entomological Society of 

 Washington at its September (1886) meeting, and we quote his account 

 of his observations : 



In the month of August, on the larger stones in parts of Eock Creek, District of 

 Columbia, where the current was swiftest, and particularly on such rocks as were 

 tilted so as to bring a portion of the surface close to the surface of the water, were 

 observed hundreds of peculiar funnel-shaped larval cases or Avebs (Plate IX, Fig 5) 

 of a species of this interesting Trichopterous genus. The cases varied greatly in size. 

 The mouth of the funnel in some instances was not more than 8"^™ in diameter and in 

 others reached fully 10""". The tube of the funnel was in every case bent nearly at right 

 angles with the mouth, and the larva ensconced within it waited for its prey to be 

 caught in the broadened mouth. It was noticed that the cases were preferably 

 placed at the edge of slight depressions in the rocky surface, so that the tubular por- 

 tion was protected from the full force of the current. The broad funnel-shaped ex- 

 pansion was woven in wide meshes with exceedingly strong silk, and was supported 

 at the sides and top by bits of twigs and small portions of the stems of water plants. 

 The central portion was so open as to allow the water to pass through readily. The 

 tube was strong and tight and was covered with bits of leaves and twigs. It was 

 open at either end. On the siu-face of a rock aljout 18 inches in diameter 166 of 

 these nets were counted. At this portion of the stream the larvae of a Simulium 

 (probably S. venustum. Say) were very abundant. They occurred chiefly on the 

 small water plants which grow in these rapid places, and were found in considera- 

 ble numbers on the surface of the rocks on which the cases of Hydropsyche occm-red. 

 They must have been washed into the mouths of these nets in great niimbers, and 



fjrobably furnished the principal food of the carnivorous larvte. The Hydropsyche 

 arvse (Plate IX, Fig. 3, and enlarged head. Fig. 4) were very active and diflficult to 

 capture, unless the stones were removed entire from the water. Placed m standing 

 water they fought vigorously Avith each other, and after a lapse of twenty-four hours 

 did not seem appreciably affected by the want of fresh water. 



Miss Cora H. Clarke has described the nets of a similar species of 

 Hydrojpsyche (Proc. Bost. Soc. Nat. Hist., vol. 22, May 24, 1882), but 

 does not mention the insects which formed the food of the larvse 

 observed by her. 



