THE NATURAL HISTORY SURVEY. 30 
VII. ECONOMY OF THE MOLLUSCA. 
While the land and fresh-water species of the area are of 
no particular economic use to man, save as bait for fishing, yet 
in an indirect way they are of great benefit to him in furnishing 
food for birds and fish. Ducks and wading birds are particu- 
larly fond of such species as Bythinella nickliniana, Amnicola 
limosa, and other small univalves, not to speak of numerous 
small forms of Pisidia and Spheria. Passerine birds are fond 
of Pupa, Vertigoand small Limaces. Fish eat mollusks as large 
as Campeloma decisum,and even extract the animal from Unios.* 
Limax campestris is said to be eaten by the red salamander 
(Plethodon erythronotus, Greeny) and it is probable that many 
animals, of whose food supply nothing is known, feed upon mol- 
lusks. It not infrequently happens that a too inquisitive animal 
gets caught in trying to obtain molluscan food, an instance of 
which passed before writer’s notice some time ago. This was a 
western painted terrapin (Chrysemys marginatus) whose right 
hind foot had been caught and tightly held by a vigorous speci- 
men of Unio luteolus. A similar case of a sora rail (Porzana 
carolina) has been noted, although the bird was probably not 
seeking the Unio for food. t 
There are many forms of mollusks (Pulmonata) which are 
hurtful to man by injuring his plants or gardens. Our green- 
houses are infested with several European species, which have 
been introduced into the country by means of imported plants. 
These are Limax maximus, L. flavus and Vitrea cellaria. In 
the greenhouses they are sought after daily and killed by being 
placed in boiling water. It is probable that many of our larger 
species prey upon cultivated fields, although the writer has not 
heard of such being the case in the present area. A good way 
to keep them out of a cultivated patch is to spread a layer of 
dry ashes, some two feet in width, around the plot of ground. 
When the mollusk meets this obstruction it will secrete mucus 
so fast that it will soon die from exhaustion. 
Will, STATISTICS. 
The following tables have been introduced to enable the 
reader to compare the molluscan fauna of this area with that of 
*See The Nautilus, Vol. V., p. 128. 
+Witmerstone, The Nautilus, Vol. III., p. 19. 
+The Nautilus, Vol. IX., p. 49. 
