AET. 20 FLORIDA TREE SNAILS — SIMPSON 17 



.special risk or hardship about this, for the snail never leaves the 

 sheltering hammock; it can stop and deposit eggs whenever it likes; 

 there is an abundance of food all around it. 



A large part of the lower Florida mainland, however, is covered 

 with an open growth of Caribbean pines, and such a region is hostile 

 to the Ligims. There is practically no shelter; there is little or no 

 food ; in places where the floor of the forest is sandy it is impossible 

 for them to progress unless they can crawl from plant to plant above 

 it. Only here and there at intervals is there a hammock, and 

 although the snails have a certain amount of vision yet it is probably 

 impossible for them to distinguish one from the pineland. Yet these 

 wanderers obey the instinct for founding colonies which was begotten 

 during the thousands of generations that preceeded them and boldly 

 strike out into the pine woods in order that they may reach another 

 hammock and plant their race in a new territory. 



At my home I once observed one of these snails which liad doubt- 

 less left my near-by hammock and was attempting to work its way 

 out into the open pine woods. We had rains for several da^'s in 

 succession, and during this time it moved away from the hammock at 

 the rate of about 25 feet a day. and I kept close watch and set stakes 

 to mark its onward passage. This one and others I have noticed 

 crawled along the stems of small shrubs or grass, over fallen logs, or 

 anything that made a firm pathway. Wlien the weather was dry and 

 the sun shone the Liguus attached itself to something and did not 

 attempt to go on until it rained again. I kept track of this specimen 

 for several days, noting that it persistently Avorked away from my 

 hammock and out into the uncharted pine woods. I have on a few 

 occasions found them in the open forest at a long distance from any 

 hammock and in rather numerous cases the dead shells which 

 probably testified to the disaster in the way of exhaustion that finally 

 overtook them. 



The migration is of course absolutely hit and miss, as no snail can 

 know when it starts on such a journey that a hammock is in front 

 of it. No doubt in cases where a number of hammocks are scattered 

 through an area of pine forest a crawling Liguus miglit pass by one 

 and, continuing on, enter another not far away. So in any general 

 region a hammock may have a form that is absent from another that 

 is only a few rods away ; one may have several subspecies and another 

 near by only two or three, even a single one, or rarely none at ail. 

 One of our leading botanists believes that the hammocks formerly 

 covered most of the lower part of Florida and that the pine trees 

 are late immigrants that are spreading and taking possession of the 

 country, but if this were true we should find the remaining hammock 

 portion occupied by practically the same forms of Liguus throughout. 

 97556—29 3 



