162 



ZOOLOGY 



in captivity by keeping in a dark box and feeding on the 

 blanched leaves of cabbage. In captivity one individual 

 will sometimes devour another. 



Of our three principal species of slugs there may be first 

 mentioned Limax maximus, which gains a length of about 

 10 centimetres and has a light brown color, marked with 

 longitudinal rows of black spots along the back and sides. 



This species was almost un- 

 known in this country until 

 the middle of the sixties, but 

 it is now widespread through- 

 out the East. It has doubt- 

 less been introduced from the 

 continent of Europe, where 

 it is very abundant. Second, 

 Limax ay rest is 1 is usually 

 about 2.5 centimetres long ; 

 it varies in color from whitish 

 through gray to black. It is 

 now common in the eastern 

 United States, but is believed 

 to have been introduced from 

 Europe. Third, Limax cam- 



genera figured are: A, Actaeon ; pestris? a native species, is 

 B, Aplustrum; C, Cylicbna; D, , , 



Atys; E, Phiiine ; F, Doiabeiia; smaller than agrestis, and 



its tuberosities are not so 

 much flattened or plate-like. 

 It occurs widely distributed 

 east of the Rocky Mountains. 



Economically, slugs are of importance because at times 

 in some localities they cause much destruction in gardens 



1 Living in the field. 2 Living in open fields. 



FIG. 149. Illustrating the transi- 

 tion of form in the shell of certain 

 Opisthobranchs, from the pointed 

 spiral to the almost tiat plate. The 



G, Aplysia ; //, Pleurobranchus. 

 Drawn to various scales. From 

 Cooke, " Mollusca." 



