114 LAND AND FRESH-WATER MOLLUSKS. 
turist, count among the former group the slugs 
and snails: even our present acquaintance, HH. 
aspersa, is regarded by them as a great pest in the 
gardens, devouring vegetables with the greatest 
avidity, and is treated accordingly. Many of these 
enemies have been mentioned ; some still remain 
to have their misdeeds published to the world. 
Those snails which derive their nourishment 
from culinary and cultivated plants belong to the 
second category. ‘The means to be employed for 
their destruction are :— 
Ist.—By the aid of their natural enemies. 
Thus many insects, especially of the genera 
Drylus, Lampyris, Staphylinus, Sylpha, attack 
the terrestrial species, and deposit their eggs in 
the substance of the snail’s body. Ducks, geese, 
fowls, thrushes, blackbirds, prey upon them; 
the hedgehog devours with avidity Helices and 
Bulimi. 
2nd.—By protecting the trees and plants from 
their attacks,—encircling them with absorbent 
powders,—washing the walls with a weak solu- 
tion of corrosive sublimate. 
3rd.—By the destruction of the eggs and 
individuals: and to do this, dig deep the soil, 
leaving it exposed to the sun, for some days, 
before consigning to it the grain and plants. The 
individuals may be decoyed, gathered, and de- 
stroyed by throwing into lime-water, &c. 
