AKGULID.*; OF THE WOODS HOLE REGION. 1 '_' 1 



host any serious inconvenience: their natural enemies keep them within due bounds 

 and every tisli has a chance to rid itself almost entirely of parasites when the latter 

 are breeding. 



•1. It' a tish becomes diseased the influence of the parasites is thereby increased, 

 so that they hasten, and may partly canst', its death. 



3. Fish while undergoing the rigorous efforts necessary to migration become 

 greatly weakened and hence more susceptible to the influence of these pests. 



4. The increased temperature of summer, especially in shallow fresh-water ponds, 

 makes the fish so inert that they often become seriously infested, and are killed in 

 large numbers. 



5. The restrictions existing in aquaria, artificial hatcheries, etc., greatly assist 

 these parasites, which speedily become a serious nuisance unless destroyed in some 

 way. 



6. Their most effective enemies are the smaller surface tish. dace, roach, etc.. 

 which eat the larvae. Some minnows (J*wndadus) will even eat the adults under the 

 constraint of hunger. 



7. The protection of these small fish and their introduction wherever possible is 

 thus one of the most practicable preventives of any serious multiplication of the 

 ArguU. 



DESCRIPTION OF SPECIES. 



KEY. 



1. Carapace orbicular, wider than long, sucking disks very large 2 



Carapace elliptical, considerably longer than wide, sucking disks relatively small 4 



2. Swimming legs of first ami second pairs with recurved flagella catostomi, p. 123 



Swimming legs without flagella 3 



3. Basal plate i if seci >nd maxillipeds with three stout teeth funduli, p. 125 



I tasal plate prolonged posteriorly as an entire lobe without any teeth lotus, p. 13s 



4. Swimming legs of first and second pail's with recurved flagella laticauda, p. 127 



Swimming legs without flagella 5 



5. Abdomen orbicular, wider than long, cut less than one-third, lobes well-rounded . .megalops, p. 129 

 Abdomen elongate, longer than wide, cut to the center, lobes lanceolate-acuminate alosse, p. 121 



Argulus alosae Gould. Male and female known. 



Carapace relatively small, elliptical, much longer than wide, just reaching to the posterior tho- 

 racic segment; posterior sinus rather narrow and becoming contracted toward the base; eyes far for- 

 ward, chitin rings in the lateral areas unequal, the smaller anterior to the larger, of nearly the same 

 diameter, but much shorter; posterior segment of thorax projecting over the abdomen in a small 

 rounded lobe on either side with a shallow sinus between; abdomen broad, elliptical, cut beyond the 

 (•enter; lobes divergent, lanceolate-acuminate; anal papilla' basal, no spines on the ventral surface of the 

 carapace; antennae rather small and poorly armed; posterior maxillipeds stout; basal plate triangular, 

 considerably raised, and prominently roughened; posterior teeth short and blunt. Swimming legs 

 reaching far beyond the carapace, without flagella; lobes on the basil joint of the posterior pair nearly 

 rectangular and relatively very small. Male with no accessory sexual organs except the usual peg and 

 semen receptacle; lobes of the basil joints of the posterior legs more pointed than in the female: 

 abdomen much elongated; testes very large. 



Color a uniform pale bluish-green with scattering pigment on the dorsal surface arranged in 

 radiating dots and lines. Length of female, 7-10 mm.; length of carapace, 4-6 mm.; breadth of 

 carapace, 3-5 mm.; length of abdomen, 2-.". mm.; breadth, 1.7-2.5 mm. Male about half this size. 

 (Description from living specimens. ) 



