BLACKFLIES 



481 



seen in Fig. 223. The breathing filaments vary greatly in dif- 

 ferent species and may have from four to 60 branches. 



The adults escape from the pupae after from one to three 

 weeks through a slit in the back, and are carried safely to the 

 surface by a bubble of air which has been collecting inside the 

 old pupal skin. The adults are short lived and lay their eggs 

 soon after emergence. The whole life of a gen- 

 eration from egg to egg may be passed in from 

 six weeks to two months or more. Some spe- 

 cies have several generations a year but the 

 majority produce but a single brood a year. 

 The Canadian species already referred to is 

 seen only for a few weeks in May and early 

 June, during which time it is locally exces- 

 sively abundant. Most species are diurnal, 

 but the author found the Ontario species to 

 be most active from late afternoon until dark, 

 and again early in the morning. This species 

 will also bite readily at night in the presence of 

 artificial light. 



The species of blackflies are numerous, but 



are all included in the single genus Simulium, O f blackfly, 



with several subgenera which some workers lium Jennino 



i . , /. , moved from 



elevate to the rank of true genera. Some 





, re- 



case: 



e ., eye; i.e., leg 



species do not attack man but viciously attack cases : br - f -> breath- 

 various domestic animals. While on a collect- w. g c! wing* case.' 

 ing trip in the Cascade Mountains of Oregon ( Af ter Jobbins-Pom- 

 the author found it necessary to keep the pack er 

 animal picketed in the smoke of the camp fire constantly to pro- 

 tect the poor creature from the blackflies which congregated in 

 large numbers about his eyes and nose, yet neither the author nor 

 his companion was ever bitten by one of these flies. One of the 

 most troublesome species in the United States is S. pecuarum, 

 the famous buffalo gnat of the south central portion of the country. 

 This species was formerly more abundant than now, and was a 

 terrible scourge to mules and cattle. S. venustum is one of the 

 most important molesters of man. It occurs over the greater 

 part of the eastern portion of North America. 



Annoyance. In the estimation of the author, no insect 

 scourge he has ever experienced is more terrible than an attack 



