FOOD, HABITS, ETC. 71 



times descend with the rain. Frequently they will 

 anticipate a downpour and climb the bushes and 

 trees in expectation of the coming rain. The colora- 

 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 specialty low tempera- 

 ture. 



Some of the freshwater Gastropods can also endure 

 great heat. Limncea 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.). 



