SIMULIUM. 57 



specimen from same locality (J. R. Malloch), and a reared series 

 from South Carolina (Jennings and King). 



Larva. — Length 9 to 12 mm. Sometimes almost entirely black in 

 color. The fans (PI. Ill, fig. 5) have about GO rays which have 

 regularly spaced seta? and slightly shorter and much finer ciliae be- 

 tween them. The mandibles are as figured on Plate III, figure 2, and 

 respiratory organs as in Plate VI, figure G. The labium has the cen- 

 tral tooth longest and in general outline approaches the veniistuiii 

 type of dentation (PI. Ill, fig. 4). So far as my experience goes — 

 and that of Messrs. Jennings and King substantiates it — the larva? 

 of this species are always found on rock surfaces where there is a 

 rapid current, such as on waterfalls, and are difficult of detection 

 owing to their dark color which harmonizes well with that of the 

 rocks. If such conditions are essential to the larvae it will account 

 for the presence of the species in certain suitable localities and its 

 absence from others where such conditions do not prevail. 



Pupa. — The respiratory filaments consist of nine branches (PI. IV, 

 fig. 2). The cocoons are slipper shaped and yellow-brown in color 

 (PL VI, fig. 8). They are placed close together on the rock surface 

 with the open ends pointing downstream. Owing to their pale color 

 and their being placed closelj^ together they are easily seen on the 

 dark surface of the rocks. It is not difficult to obtain imagines from, 

 the pupoe if they are kept on damp — not wet — cotton. 



The adult female will bite horses, but there is no published record 

 of its attacking human beings that I can find. One specimen in the 

 collection of the U. S. National Museum from Plummers Island, Md., 

 November 3, 1901, bears a label with the word "biting," but Mr. 

 H. S. Barber, who took the specimen, does not recollect the particu- 

 lars of its capture. 



Simulium virgatum Coqulllett. 



Female. — Black-brown, opaque. Frons and face with thick 

 whitish gray dusting; antenna? brown, the two basal joints yellow; 

 palpi black-brown. Scutum distinctly striped, central stripe nar- 

 row, linear, lateral pair curved, the anterior dilated portion filled 

 with white pollinosity forming a pear-shaped spot, the anterior angle 

 of which is as broad as the space between the spots ; lateral margins 

 darkened; pleura? distinctly white-dusted, scutellum concolorous with 

 scutum; postscutum witli white silky pollinosity. Abdomen black- 

 brown, opaque on basal four segments, subshining on apical four, all 

 segments with distinct, narrow, white-pollinose fascia? on hind mar- 

 gins. Legs yellow, brown, or black-brown, as follows: Apices t)f 

 femora, a narrow ring or spot at bases and apical halves of all tibia?; 

 entire fore tarsi; apices of first and second and remaining joints of 



