100 MOLLUSC A, INSECTS, ETC. 



nalis and L. pereger, it is far from rare. Its habits 

 are very similar to L. stagnalis, except that it is 

 fonder of confervoid vegetation ; and as this always 

 tends to become a pest, auricularia is therefore a 

 valuable addition to a fresh-water tank. Stagnalis 

 has an undue preference for certain of the higher forms 



Fig- 47- Fig. 48. 



Limnea 



Limnea auricularia. pereger. 



of aquatic vegetation, notably Vallisneria ; and if 

 there be any of this plant present it will surely feed 

 on it in preference to any other. When Vallisneria 

 is too rank in its growth these molluscs may there- 

 fore be employed to temporarily keep it down. 



Limnea pereger (Fig. 48) is the most abundant of all 

 our native species, and, as is commonly the case with 

 species that are individually numerous, it has given 

 rise to at least fourteen well-marked varieties. It is 

 more active in its movements than the species already 

 noticed, and likes occasionally to creep out of the 

 water up the stems of aquatic plants for a temporary 

 breath of fresh air. It is exceedingly prolific, Dr. 

 Gwyn Jeffreys stating that it lays about thirteen 



