FOOD, HABITS, ETC. a1 
times descend with the rain. Frequently they will 
anticipate a downpour and climb the bushes and 
trees in expectation of the coming rain. Thecolora- 
tion of the bodies, too, at these times is said in 
certain species to undergo a change. 
It has been supposed that excess of moisture will 
produce melanism in terrestrial Mollusca, but this is 
far from certain; cold, and possibly the nature of 
their food, having apparently more to do with the 
phenomenon. 
Given moisture, temperature seems no drawback, 
and they become innured to very opposite extremes, 
though cold affects them less than heat. For those 
inhabiting high latitudes cold means a corresponding 
diminution in the period of activity, and Snails at 
Point Barrow, Alaska, must remain in a state of 
hibernation at least nine months in the year, and 
this probably has more effect on the animal than the 
mere occurrence at times of a specially low tempera- 
ture. 
Some of the freshwater Gastropods can also endure 
great heat. Limnaa pereger has been taken in a hot 
spring in Iceland where the water reached a tempera- 
ture of 40° C. (=104° F.), while 50° C. (=122° F.) 
has been cited for Paludestrina thermalis at Abano. 
Certain of the Land Snails can also survive great 
heat. A living specimen of Helix lactea was picked 
up in the Sahara, where the ground temperature was 
50° C. (=122° F)). 
