SOME PARASITES OF SIMCLITM LARY.K AND THEIR 

 EFFECTS OX THE DEVELOPMENT OF THE HOST. 1 



E. H. STRICKLAND, 

 CARNEGIE SCHOLAR IN ECONOMIC ENTOMOLOGY. 



During the spring of the present year (1911) while studying 

 entomology at the Bu^rv Institution of Harvard University, 

 I made numerous collections of Simulium larva 1 , which arc 

 extremely abundant in the neighboring streams, with the in- 

 tention of studying the development of the imaginal discs which 

 are unusually well defined in this genus of diptera. As, however, 

 I found that a large percentage of these interesting larvae were 

 heavily parasitized by two very different organisms, namely a 

 worm and a protozoon, I turned my attention rather more 

 directly to these and their effects on their hosts, during the feu- 

 weeks intervening between my first discovery of the parasites 

 and the pupation of the insects. 



Before giving any details I wish to take this opportunity to 

 offer my sincere thanks to Professor Wheeler, who by his kind 

 suggestions and advise enabled me to bring together the fol- 

 lowing facts, which, though very incomplete in form, do not 

 appear to have been recorded before. My thanks are also due to 

 Professor Johannsen for naming the species of Simnlinni larvae 

 and to Professor T. H. Montgomery who identified the worm 

 parasite as a species of Mermis. 



LIFE HISTORY AND STRUCTURE OF SIMULIUM LAUV.E. 



A brief summary of the structure, and mode of life, of the 

 Simulium larva? may not be out of place here. 



If during the months of March to May one examines the rocks 

 or vegetation in any swiftly flowing stream in the neighborhood 

 of Forest Hills, Mass., especially where ii-> bed causes a small 

 cascade, one will, in all probability, observe a large, dark, 

 gelatinous mass where the current is >\\ittest and the water 



'Contributions from the Entomological Laboratory <>\ the llni \ Institution, 



Harvard University, No. 45.) 



302 



