226 SANITARY ENTOMOLOGY 



usually extended in running water. They function both as blood gills 

 and tracheal gills. The structure of these gills affords characters of 

 value for the identification of the species. 



The larvae attach themselves by the caudal suckers and float in the 

 stream, catching their food by means of the fan-like processes on the 

 head. When disturbed, or if the stream diminishes, the larva* let them- 

 selves float down the stream attached by a silken thread to a permanent 

 object, by which they can regain their former position. When about to 

 pupate the larva spins over itself a pocket-shaped pupal case. The 

 pupae are provided with respiratory organs on each side of the thorax. 

 These are composed of long chitinous tubes with a single main stalk and 

 four or more divisions. Good specific characters for identification are 

 found in the structure of these respiratory organs (plate XV). 



The development period of Simulium in South Carolina is about 7 

 days for the egg, 17 days for the larvae, and 4 days for the pupae. The 

 number of generations depends upon the species and the season and may 

 range from one to six or more generations. 



FAMILY PSYCHODIDAE 



Pappataci Flies 



The owl midges are small moth-like flies. Only the genus Phlebotomus 

 contains bloodsucking flies, Which are often called sand flies. T!h,d 

 pappataci fly, Phlebotomus papatasii Scopoli, cause of pappataci fever; 

 P. minutus Rondani, a possible carrier of Bagdad sore, and P. ver- 

 rucarum Townsend, supposed carrier of verruga, are the only species 

 definitely charged with carriage of disease. Only the females suck 

 blood. They deposit their eggs in damp, dark places, in clusters or 

 singly, to the number of from 30 to 80. The eggs are covered with a 

 thin coating of a sticky substance which causes them to adhere to any 

 surface. They are very elongate, dark bro\vn, with longitudinal, black, 

 wavy lines. The incubation period is from six to nine days. The larvae 

 live in damp earth. They are very peculiar, having large, well marked 

 heads with big jaws, which have four distinct teeth. The body is covered 

 with toothed spines and the posterior end bears two pairs of very black 

 caudal bristles, one pair of which are as long as the body. The larva 

 feeds on semi-decaying vegetable matter. The pupa is remarkable for the 

 large ridges and excrescences on its thorax. The larval skin usually 

 remains adhering to the caudal extremity. 



These flies breed in crevices of stone walls and fissures between rocks 

 in caves, in dirty, damp cellars, and on the damp walls of latrines and 

 cesspools, and wherever there is damp ground in dark places. Lizards fre- 



