THE CANADIAN' liXTU.MULOGIST 405 



5. Female moth, bred- specimen showing extended ovipositor. 



6. Pemale moth, bred specimen, side \ie\v. 



7. Female moth, specimen found on ix)phir. 



8 ] 



^ j Male moths; bred specimens. 



10. Male moth, collected at Winnipeg, Man. 



11. Male moth, collected at Aweme, Man. 



SOME PARASITES OF SIMULIUM LARV.F: AND THEIR 

 POSSIBLE ECONOMIC VALUE.* 



BV E. HAROLD STRICKLAND, DIVISION OF ENTOMOLOGY, OTTAWA. 



During a year's residence at the Bussey Institution of Harvard 

 University, in 1911, the writer had an opportunity of studying the 

 Simuliid larva? which abound in the streams of that locality. This 

 study revealed the fact that a large percentage of these larvie are 

 attacked by parasites, the presence of which appears to result, in 

 all cases, in the death of the host. Simuliid larvae are most abun- 

 dant in these. streams from early March until May. Isolated speci- 

 mens are found from then onwards till October, when other species 

 occur in considerable numbers upon the rocks and" vegetation in 

 rapidly flowing parts of the streams. 



A brief resume of the peculiarities in structure and habits of 

 these interesting larvcC will be of advantage here, as their curious 

 modifications have a very direct bearing upon their liability to 

 parasitism. 



The larvcC are to be found either solitarily or gregar'ously, 

 according to species, attached by means of a caudal sucker to 

 stones or vegetation, only in the fastest flowing water. Silken 

 threads secreted from the salivary glands act as anchor lines, hold- 

 ing the lar\a in a vertical position, and retain a hold upon the 

 support should the caudal sucker become detached. The cylin- 

 drical head bears on its anterior border two fan-like organs carried 

 on elongate pedicels. When expanded, these fans form two very 

 efficient bowl-shaped, strainers, through which the water flows. 

 They can be closed at .will, and brought over the mouth orifice, 

 carrjang with them the small particles of vegetation, and diatoms 

 which constitute the food of the larva\ Since Simuliid larvae, 



*Conlributions from the Division of Entomology, Ottawa. 

 December, 191.3 



