— 168— 



whether it comes from southern New Mexico, from south-eastern 

 Arizona, or from Sonora. The Morrison collection, for instance, has 

 been distributed among North American entomologists as coming from 

 south-eastern Arizona and is worked up in the " I-)it)logia Centrali- 

 Americana" as coming from Sonora, Mex. 



Returning to Florida and the West Indies we find a quite different 

 state of affairs. Florida is apparently well separated from Cuba, the 

 nearest of the West Indian islands, by an ocean which, at its narrowest 

 place, is 90 miles wide. In realty, however, this wide arm of the ocean 

 does nut separate but c>innects the West Indies with Florida ; in lact it 

 is not an ocean but the mightiest river on this globe, with a strong 

 current : in short it is the Gulf stream. As everyone kmiws, the valleys 

 of large streams are most favorable for distributing different faunas. 

 Take the Mississippi River ior instance : it has often been pointed out 

 that along its banks and its valley the fauna and flora of the Southern 

 States extends well up into the Norihern States as far as Iowa and 

 Nebraska, while the current of the river constantly carries numerous 

 species of northern plants and insects into the Southern States. The 

 Gulf stream has neither banks nor a valley and a distribution or migra- 

 tion against the current or up stream is not possible but a distribution 

 with the current takes place as in any other large, river. The result is 

 that Floridian insects and plants cannot migrate southward into the 

 West Indies, while numerous species of West Indian plants and insects 

 are easily carried with the current on to the shores of Florida where the 

 insects find a permanent lodgement because their original food-plants 

 have also established themselves at the same place. 



In looking for the original home of this colony of West Indian in- 

 sects and plants we have been hitherto too much accustomed ta con- 

 sider the island of Cuba as the only place from which this immigration 

 has taken place. In the task of determining my South Floridian Co- 

 leoptera it was found over and over again that these immigrants may 

 have been described not only from Cuba, but from any other of the 

 West Indian islands, or from the Central American continent south of 

 Yucatan, or even from Columbia and Venezuela — in other words from 

 all parts of Central America which come under the influence of the Gulf 

 stream. As can be seen from any physical atlas, the warm equatorial 

 current enters the Caribbean sea through the Windward Islands and at- 

 taining by this contraction a considerable velocity forms the Gulf stream 

 which flows between the southernmost chain of the West Indies and 

 the Leeward Islands and strikes the Central American continent, flow- 

 ing northward along the coast. Deflected by the projecting peninsula 

 of Yucatan, the stream turns eastward and reaches the coast of Cuba 



