The Nautilus. 



Vol. XIV. JUNE, 1900. No. 2. 



.ESTIVATION OF EPIPHRAGMOPHORA TRASKII IN SOUTHERN 

 CALIFORNIA. 



BY MRS. M. BURTON WILLIAMSON. 



When the frost is on the ground and autumn leaves lie scattered 

 over orchards and forests, it is no surprise to find that land snails 

 (Helices) have begun their period of hibernation, and lie sheltered 

 under the layers of dead leaves or hidden in decaying trunks of trees. 

 The annual sleep of the snail in winter corresponds well with the 

 enforced rest of the vegetable world ; but in a tropical or semi- 

 tropical climate the atmospheric conditions are different, and in place 

 of a winter rest, snails take their annual sleep in summer. The 

 hibernation of snails in colder countries is reversed, and in its stead 

 aestivation of snails is the result. In the eastern states helices take 

 their annual siesta in winter, but in southern California snails differ 

 from their congeners, presenting an illustration of the power of en- 

 vironment in modifying instincts. Instead of going into winter 

 quarters in October and remaining from four to six months without 

 food and motionless, the greatest activity of the southern California 

 Helix is during the winter months. The reason for this is that the 

 food supply is plentiful in the winter when the warm rains prevail ; 

 and during the summer months the arid condition of the foot-hills, 

 the habitat of these quiet creatures, made the aestivation of snails a 

 necessity, a question of economy, an adjustment of demand and 

 supply. In process of time the necessity for aestivation rather than 

 hibernation became a habit. 



When snails require rest in southern California they attach them- 

 selves to the under surface of dead cacti, pieces of wood, stones, or 



