SIMULIUM. 55 



S. trihidaficm, deals at some length -with its habits. Its distribution is 

 quite the widest of any of the American species. It may be that 

 there are more than one species in the material l)efore me, but I can 

 not find any characters to separate the xVlaskan specimens from those 

 of Mexico. Argus Williston is, I consider, identical with vittatum. 

 Sometimes the thorax gets wet and the stripes, being visible only 

 through the presence of the pollinosity in good specimens, become 

 indistinct or practically invisible. There is nothing strange in the 

 fact that they are not mentioned in Williston's original description of 

 his species, if his specimen was not in good condition. 

 The larva, as described bv Johannsen, is as follows: 



Somewhat mottled gray, the sides of each segmeut blackish. The head is 

 of the usual reddish brown color; the pale yellow antouiue long and cylindrical, 

 the second joint about one-third the length of the first, the third is a pointed 

 process at tip of the second. The fans have about 40 rays, the cilia being 

 relatively minute. The mandibles are provided with three large apical teeth 

 besides the row of secondarj^ ones; the apical pair of bristles is present. The 

 maxillary palpus has a few spines, and a tuft of a few spines on the basal 

 joint. * * * The labium has an elongated middle tooth, those at the end 

 nearly as long, the intermediate ones short, and thei'e are six bristles in each 

 of the two longitudinal rows on the ventral surface. The three blood gills at 

 caudal end are unbranched. 



The pupal respiratory organs are as shown in Plate IV, figure 4. 



The cocoon is similar to that of venustum Say, and is attached to 

 leaves or plant stems in the water. Occasionally there are only 15, 

 instead of 10, filaments in the respiratory organs. I have seen the 

 pupa^ from Spartanburg, S. C, (Jennings and King). 



Simulium pictipes Hagen. 



Female. — Dark gray, opaque; frons and face very thickly white- 

 dusted; antenna^ brown, j'ellowish on basal two joints; palpi brown- 

 black. Scutum thickly graj'-dusted, with three brown or black 

 stripes, the central one straight, the lateral ones curved, and dilated 

 slightly anteriorly, the dilated portion with white pollinose spot 

 when viewed from behind ; pleura? gray, opaque ; scutellum and post- 

 scutum concolorous. Abdomen gray, segments 2-4 broadly opaque 

 brown or black-brown on dorsum, the one below basal scale only 

 slightly darker on center. Legs dark gray, only the bases of tibiae 

 and bases of first tarsal joints of mid and hind legs paler, except in 

 immature specimens, when the legs may be yellowish, but they never 

 >-how so distinctly bicolored as in rivgatinn or Jn/nter!. "Wings gray- 

 ish, the veins rather more distinct than usual. Halteres yellow, 

 darker at base of stalk. 



Frons slightly raised in center, divergent-sided, as long as broad 

 at upper angle of eyes, where it is one-fourth wider than at lower 

 angle of eyes; surface hairs white, with a sliglit admixture of black 



