NORTH AMERICAN PARASITIC COPEPODS BELONGING 

 TO THE FAMILY ERGASILID^. 



By Charles Branch Wilson, 



Department of Biology, State Normal School, Westfield, Mass. 



INTRODUCTION. 



The present is the tenth'* paper in the series based upon the collec- 

 tion of parasitic copepods in the U. S. National Museum, and deals 

 with the family Ergasilidse. 



As in all the preceding papers, the Museum material has been 

 largely supplemented by a study of living forms, developmental 

 stages, and material derived from other sources. 



Much of this study has been accomplished while working for the 

 U. S. Bureau of Fisheries at various laboratories situated both 

 upon salt and fresh water. For these valuable opportunities the 

 author is indebted to the courtesy of the Hon. George M. Bowers, 

 U. S. Commissioner of Fish and Fisheries, to whom acknowledgment 

 is gratefully made. 



Thanks are also due to Prof. E. A. Birge and Prof. Chauncy Juday, 

 of the University of Wisconsin, for furnishing a generous supply of 

 tow taken from Lake Mendota, Madison, Wisconsin, from which has 

 been obtained an excellent series of specimens of both sexes of 

 Ergasilus cliautauquaensis. 



The value of this material is enhanced by the fact that it was the 

 first opportunity for a personal examination of an Ergasilus male. 



To Dr. Andrew Scott, of the Board of Fisheries of Scotland, the 

 author returns sincere thanks for some finely preserved specimens of 



oThe nine preceding papers are 1. The Argulidse, Proc. U. S. Nat. Mua., vol. 25, 

 pp. 635-742, pis. 8-27. 2. Descriptions of Argulidse, idem, vol. 27, pp. 627-655, 

 38 text figures. 3. The Caliginse, idem, vol. 28, pp. 479-672, pis. 5-29. 4. The 

 Trebinse and Euryphorinse, idem, vol. 31, pp. 669-720, pis. 15-20. 5. Additional 

 Notes on the Argulidse, idem, vol. 32, pp. 411-424, pis. 29-32. 6. The Pandarinse 

 and Cecropinse, idem, vol. 33, pp. 323-490, pis. 17-43. 7. New species of Caliginse, 

 idem, vol. 33, pp. 593-627, pis. 49-56. 8. Parasitic Copepods from the Pacific Coast, 

 idem, vol. 35, pp. 431-481, pis. 66-83. 9. Development of Achtheres ambloplitia 

 Kellicott, idem, vol. 39, pp. 189-226, pis. 29-36. 



Proceedings U. S. National Museum, Vol. 39— No. 1788. 



263 



