NO. 7 PROTECTIVE ADAPTATIONS McATEE IO9 



very long list of squid-eaters. As to the extent to which these cephalo- 

 pods are taken, Field reports squid from the following percentages 

 of the stomachs examined by him : Summer skate 6.39 per cent, 

 smooth dogfish nearly 10 per cent, and goosefish 17.39 per cent. 

 Cuttlefishes are known to be eaten by the bonito. c(xl, whiting, and 

 gurnard, and octopods by the ling, haddock, and conger eel. 



Turning to the fresh-water mollusks, we find that they are equally 

 beset by enemies. Pearse reports 2 per cent of the total food of 

 32 species of fishes in Wisconsin lakes consists of these animals, and 

 from Forbes we learn that mollusks make up about one- fourth of 

 the food of the dogfish (Aniia) and a sheepshead (Aplodinolus) , 

 about half that of the suckers (Cofostoniiis), rising to 60 per cent in 

 the case of the red-horse (A^coxostoiua), and a considerable propor- 

 tion (14 to 16 per cent) of the food of the perch (Pcrca flavcsccns) , 

 catfishes, sunfishes, top minnows, and shiner {Ahroiiiis) . Almost all 

 fishes eat mollusks to some extent and practically all groups of 

 mollusks suffer from these predatory attentions. 



Taking up the relations of amphibians to mollusks, it may be noted 

 that Kirkland found i per cent of the food of 149 toads to consist of 

 snails and slugs, and Drake found 29 of these mollusks in 209 

 stomachs of the leopard frog. In general it may be said that most 

 frogs consume aquatic snails when in the larval state and land snails 

 when adult. With reference to European conditions, Cooke adds : 

 " Frogs and toads are very partial to land mollusca. A garden at- 

 tached to the Laboratory of Agricultural Chemistry at Rouen had been 

 abandoned for three years to weeds and slugs. The director intro- 

 duced 100 toads and 90 frogs, and in less than a month all the slugs 

 were destroyed." (Cambridge Nat. Hist., vol. 3, p. 58, 1895.) Snails 

 are eaten by most salamanders, the kind, whether water or land, 

 depending on the habits of the salamanders concerned ; small mussels 

 even are consumed by some of tlie thoroughly aquatic forms. 



Reptiles do not prey very extensively u])on mollusks, yet snails are 

 frequently eaten by lizards ; slugs and snails are eaten by several 

 species of snakes and by most turtles, the aquatic forms of the latter 

 group consuming some bivalves. 



Among mammals we find that some of the land forms consume 

 mollusks to a slight extent ; shrews, rats, white- footed mice, s(]uirrels, 

 and chipmunks may be mentioned as examples : a specimen of the 

 eastern chipmunk (Eufamias sfriatiis) taken near Fairfax, \'a., had 

 ])acked in its cheek-pouches or swallowed more tlian 47 I\)maliof>sis 

 lapidaiia. It is well known that the muskrat preys extensively upon 

 fresh-water mussels, and the mink and otter must be listed as foes of 



