3 04 THE STUDY OF INSECTS 



slate is passed (Fig. 527). This cocoon is firmly fastened to the rock 

 upon which the larva has lived or to other cocoons, for they occur in 

 dense masses, forming a carpet-like covering on the 

 rocks. The pupa breathes by tracheal gills which are 

 borne on the prothorax. 



The adult fly, on emerging from the pupa-skin, 

 rises to the surface of the water and takes flight at 

 once. Soon after this the eggs are laid. Sometimes 

 the eggs are laid under water attached to rocks and 

 sometimes on blades of grass, twigs or leaves which 

 are dipping in the water. 

 527- — cocoon and flie females of many species suck blood and are 

 well-known pests. Unlike mosquitoes and midges, the 

 black-flies like heat and strong light. They are often seen in large num- 

 bers disporting themselves in the brightest sunshine. 



The species that have attracted most attention in the United States 

 are the following. 



The Adirondack black-fly, Prosimulium hirtipes, is a widely distributed 

 species but it has attracted most attention in the mountains of the 

 Northeastern States, where fishermen find it to be a scourge in May and 

 June. In this species the radial sector is distinctly forked. 



The southern buffalo-gnat, Eusimulium pecudrum, is the " Buffalo- 

 gnat " of the Mississippi Valley, which in the past has been a terrible 

 pest of mules and other domestic animals, sometimes causing their death ; 

 but it seems to be much less common now than in former years. In 

 this species the radial sector is very indistinctly forked at the apex. The 

 popular name of this insect refers to a fancied resemblance in the shape 

 of the insect when viewed from one side to that of a buffalo. 



The turkey-gnat, Simulium meridiondle, closely resembles the pre- 

 ceding in habits, infesting all kinds of domestic animals, especially in the 

 Mississippi Valley. As it appears at the time that turkeys are setting 

 and causes great injury to this fowl, it is commonly known as the 

 turkey-gnat. In this species the radial sector is not forked. 



The white-stockinged black-fly, Simulium veniistum, is widely dis- 

 tributed and is one of the more common species of the genus. It can be 

 distinguished from the other species mentioned here by the fact that the 

 tibiae are silvery white above. In the Adirondacks it appears later than 

 Prosimulium hirtipes and is not so serious a pest. Professor Needham 

 writes: " Guides have a saying, that, when the black-flies put on their 

 white stockings in June, the trouble is about over. This species has the 

 white stockings." 



The innoxious black-fly, Simulium pictipes, is very widely distributed 

 and at Ithaca it is our most common species. 



Family Blepharocerid^ 

 The Net-winged Midges 



The net-winged midges are extremely remarkable insects; for in 

 certain respects the structure of the adults is very peculiar, and the larvae 

 appear much more like crustaceans than like insects. 



The adults are mosquito-like in form; but they differ from all other 



