192 INTRODUCTION. 
All the species are nocturnal or semi-nocturnal in their 
habits. In the day-time they seek such shelter as may 
be at hand, and retreat into dark holes and crevices, or 
hide themselves under the fallen trunks of trees, frag- 
ments of wood, leaves and stones, or bury themselves 
wholly or partially in the earth. There they remain 
inactive until evening twilight, when, except in seasons 
of drought, they sally forth in numbers ; and in favorable 
situations, such as ravines and low places in the forest, 
may be seen crawling over the surface of the ground, 
and sometimes climbing the stalks of plants, and the 
trunks of trees. They are probably active during the 
whole night, during which they all seek their food, and 
those species which are noxious to man commit their 
depredations in the garden and orchard. At this time 
too, their sexual meetings take place. Soon after day- 
light, they retire to their retreats, and remain very close 
until night approaches again. They also come forth 
when the atmosphere is charged with moisture, and after 
light showers. 
There is a difference in the places of their retreat. 
The Limacidce are oftenest found attached to the lower 
surface of wood and stones lying in contact with the 
ground, or to the damp walls of cellars, and, in the forest. 
concealed under logs. So soon as, from the increased 
dryness of the atmosphere, these places no longer retain 
moisture, they abandon them for others, and in seasons 
of drought they penetrate deeply into the earth. The 
Helicidce, in the forest, are observed under prostrate 
