A«T. 20 FLORIDA TREE SNAILS — SIMPSON 3 



THE GENUS LIGUUS IN FLORIDA 



The genus Liguus includes about a dozen species of large land 

 snails inhabiting the northern and northwestern parts of South 

 America, the island of Cuba, Haiti, Cozumel, off the eastern coast of 

 Yucatan, and the more tropical part of Florida. The six species 

 which inhabit the islands and Florida are brightly colored and 

 strictly arboreal in habits, and they doubtless constitute a well-defined 

 subgenus. 



Cuba is an old island, geologically speaking, and has doubtless 

 been inhabited by Liguus for a long time, possibly back into the 

 Miocene. It is quite likely that the genus extended into Haiti at a 

 time when the land was much more elevated than it is to-day and 

 that island and Cuba were united. 



Although Florida is separated from Cuba by a deep channel 90 

 miles wide it seems certain that it has derived all its Liguus stock 

 from that island. At first one would naturally wonder how it was 

 possible for these arboreal snails to cross such a body of ocean and 

 become established on the new land. Both eggs and snails sink at 

 once in water; no bird could possibly carry either across in its beak 

 or on its body; neither could eggs or snails be transported through 

 the air by hurricanes. The main current of the Gulf Stream which 

 sweeps up past the western end of the great island turns to the west 

 as it enters the Gulf of Mexico and slowly passes around its deep 

 central basin. It is probable that under ordinary circumstances 

 weeks would elapse before any floating object that passed into this 

 great vortex through the Yucatan Channel would emerge and enter 

 the Florida Strait, and in that time any LiguufS which might be car- 

 ried over this course attached to limbs or trunks of floating trees 

 would be sure to be washed off and perish. It would seem, then, that 

 every means of transportation for these snails was shut out and that 

 it would be impossible for them to migrate in any way from the great 

 island to Florida. But when we once fully understand all the condi- 

 tions it appears as though nature had specially arranged everything 

 not only to make this voyage and colonization possible but abso- 

 lutely feasible and that there have been a considerable number of 

 successful migrations and colonizations. 



The Liguus never voluntarily leave the trees on which they live 

 except at the time when they go down to lay their eggs or make the 

 migrations across the country for the purpose of founding new 

 colonies, which I shall later describe. During the dry season, from 

 November to May, in Haiti, Cuba, and Florida, these snails throw 

 out a gummy substance which hardens and attaches the shells so 

 firmly to the trees on which they live that they will often break with- 

 out letting go. At this period of aestivation, as it is called, the 



