BRANCHIURA ARGULIDAE 



77 



position. They are ectoparasites upon various species of fish, 

 Argulus foliaceus being common in the fresh waters of Europe, 

 infesting the branchial chamber or the skin of fresh-water fish, 

 but being frequently taken swimming freely in the water. 



Fig. 48. — Argtdus foliaceus, young J, x 15. a^, «-, First and second antennae ; ab, 

 abdomen, £, componnd eye ; /, liver ; m, mandibles and first maxillae ; 7iix, second 

 maxilla (the median eye is seen between the two second maxillae) ; mxp, maxilli- 

 pede ; s.g, shell-gland ; sp, spine ; t, testis ; 1, 4, first and fourth swimming 

 appendages. (After Claus.) 



Both males and females can swim with great agility, and they 

 leave their hosts regularly at the breeding season in spring and 

 autumn ; fertilisation is internal, and the female deposits the 

 eggs on stones and other objects. After leaving its host, an 

 Argulus, if it cannot find a fish of the same species, can live 

 on almost any other species, and may even attack Frog tadpoles ; 

 while the kinds that infest migratory fish can change with their 



