340 



A COURSE ON ZOOLOGY. 



CHAPTER XXXIV. 

 Some Useful Invertebrates Pisciculture. 



MANY invertebrates are used as food ; among the crus- 

 tacea, such are the lobster, crab, and crayfish ; among 



MOUTH-ORGANS OF HONEY-BEE (Apis mettiftca) (largely magnified). a, tongue ; 

 b, b, labial palps ; c, c, first maxillae. 



mollusks, the oyster, clam, mussel, and scallop. Others 

 are used in medicine, such as the leech and the can- 

 tharides. In studying the various species, we have 

 already noticed this utility, and in the present chapter 

 we will consider a few insects that have a considerable 



