NORTH AMERICAN PARASITIC COPEPODS BELONGING 

 TO THE FAMILY DICHELESTHIIDAE. 



By Charles Branch Wilson, 

 Department of Biology, State Normal School, Westfleld, Massachusetts. 



INTRODUCTION. 



This is the sixteenth '^ paper in the series dealing with the parasitic 

 copepods in the collection of the United States National Museum, 

 and comprises the family Dichelesthiidae. 



The genera belonging to this family are closely related to the 

 Caligidae and Lernaeiclae and are included with them in the group 

 known as the Caligoida. They are gill parasites and when fully 

 developed the females probably remain attached to the same spot 

 on the gills of their host. In this sense they may be properly called 

 fixed parasites, but they never burrow into the tissues of the host 

 after the manner of the Lernaeidae, and yet one of the genera, 

 C'aetrodes, furnishes a very respectable compromise in this direc- 

 tion. While it does not itself burrow into the gill filament of its 

 host, it does in some way so irritate the gill epithelium that the 

 latter grows up into a flap or fold, entirely surrounding the body of 

 the copepod and holding it securely in place. 



Also other genera, such as Anthoso77ia, Eudactylina^ Nemesis.^ and 

 Dichelesthiuni, produce enough irritation with their prehensile claws 

 in the gill epithelium to cause it to grow up around the claws them- 

 selves, but so far as known it never surrounds any portion of the 

 copepod's body, not even the anterior margin of the head. In con- 

 sequence of thus remaining at least partially free there is no instance 

 of any material change in the parasite's bodily form or structure sub- 



* The fifteen preceding papers, all of which were published in the Proceedings of the 

 United States National Museum, are : 1. The Argulidae, vol. 25, pp. 635-742, pis. 8-27. 

 2. Descriptions of Argulidae, vol. 27, pp. 627-655, 3S test figures. 3. The Caliginae, 

 vol. 28, pp. 479-672, pis. 5-29. 4. The Trebinae and Euryphorinae, vol. 31, pp. 669-720, 

 pis. 15-20. 5. Additional Notes on the Argulidae, vol. 32, pp. 411-424, pis. 29-32. 

 6. The Pandarinae and Cecropinae, vol. 33, pp. 323-490. pis. 17-43. 7. New Species of 

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

 vol. 35, pp. 431-481, pis. 66-83. 9. Development of Achtheres ambloplitis Kelllcott, 

 vol. 39. pp. 189-226. pis. 29-30. 10. The Ergasilidae, vol. 39, pp. 263-400, pis. 41-60. 

 11. Descriptions of New Genera and Species, vol. 39, pp. 625-634, pis. 05-68. 12. De- 

 scriptions of New Species, vol. 42, pp. 233-243, pis. 30-34. 13. The I;ernaeopodidae, 

 vol. 47, pp. 565-729, pis. 25-56. 14. The Lernaeidae, vol. 53, pp. 1-150, pis. 1-21. 

 15. The Sphyriidae, vol. 55, pp. 549-604, pis. 50-59. 



No. 2400.— PROCEEDI NGS U.S. NATIONAL MUSEUM, VOL. 60, ART. 5. 



1 



