ARGULUS. 171 



Into what parts is it divided? Count the number of segments. 

 Look for evidence of fused segments. Notice how the spines on 

 the abdomen are arranged. 



3. Do you find eyes that are equivalent to the usual arthro- 

 pod eyes? Do you find an eye-spot? If such a spot is found, 

 determine its position and shape. 



4. Which pair of antenna is largest? Why are the large 

 antennae fringed with spines? 



5. Are there thoracic or abdominal appendages? Are any 

 appendages other than the first antennse used in swimming? 



6. The mouth parts consist of mandibles and two maxilla?. 



7. If the specimen is a female it may have two large egg sacs 

 attached to the sides of the base of the abdomen. The female 

 has two of the abdominal segments fused. In the male the seg- 

 ments are free. 



A drawing of the specimen is desirable. 



Sharpe : Notes on the Marine Copepods and Cladocera of Woods Hole and 

 Adjacent Regions, Including a Synopsis of the Genera of the Harpocti- 

 coida. Proc. U. S. Nat. Mus., 38, 1910. 



Wheeler: Free-Swimming Copepods of the Woods Hole Region. Bui. 

 U. S. Fish Com., 19, 1899. 



ARGULUS. (Fish-Louse.) 



These animals may be found on many species of fresh-water 

 and marine fish. Notice their shape and determine how they 

 cling to their host. Are they able to crawl? Can they swim? 



Find: 



1. Into what regions can the body be divided? 



2. The eyes, the eye-spot, and the two pairs of small antenna?. 



3. The sucking proboscis, composed of mandibles and max- 

 illa?, which lies between the suckers. 



4. The suckers, which are the modified second maxilla?. 



5. The posterior (third) maxillipeds just behind the suckers. 



6. Four pairs of biramous thoracic appendages. What is 

 their function? 



Make a drawing of the animal. 



Wilson : The Fish Parasites of the Genus Argulus Found in the Woods Hole 

 Region. Bui. U. S. Bur. Fish., 24, 1904. 



