178 MICHIGAN SURVEY, 1908. 



Caribbean Sea through the Windward Islands and attaining by this contraction 

 a considerable velocity forms the Gulf Stream which flows between the southern- 

 most chain of the West Indies and the Leeward Islands and strikes the Central 

 American continent, flowing northward along the coast. Deflected by the project- 

 ing peninsula of Yucatan, the stream turns eastward an-d reaches the coast of 

 Cuba and the southernmost part of Florida. Thus the West Indian colony of 

 insects in Florida may come from any part of this vast area swept by the Gulf 

 stream, although the largest proportion comes of course from Cuba since this 

 island is the nearest to Florida. This immigration by the aid of the Gulf stream 

 explains the following interesting phenomenon in geographical distribution. We 

 have seen that insects from the coast of Central America south of Yucatan may 

 occur in Southern Florida; but the same species often had the power of extending 

 their geographical distribution northward on the Central American mainland 

 through Mexico, thus reaching the south-eastern limits of the United States. 

 Certain species may occur, therefore, in the United States, in Western Texas 

 or South-eastern New Mexico and in Southern Florida, being however, 

 absent in the intervening Southern States, viz: Eastern Texas, Louisiana, 

 Alabama, Georgia, and Northern and Central Florida. This curious distribution 

 has never been pointed out so far as I am aware but can be exemplified by num- 

 erous species, not only among the Coleoptera but also other Orders of insects. 



"The distance between Cuba and Florida is not very great, the current of the 

 <Gulf stream is very swift, and logs and other debris swept out to sea from the 

 rivers of Cuba may reach the coast of Florida within three or four days; from 

 Yucatan in about double that time. It is evident that within that short time all 

 •such insects %iay safely be carried from the West Indies to Florida which, in the 

 imago or preparatory stages, live under bark, or within the wood of trees, or 

 within seeds and similar sheltered conditions, or whose eggs are firmly attached 

 to trees and covered with viscous liquid. But it is evident that this sea voyage 

 is too long for all such insects as do not live in such sheltered positions. As a 

 ■consequence, all adephagous Coleoptera, further all those living under old leaves, 

 In the ground, in very rotten wood and similar places, and finally most of the 

 Chrysomelidae which lay their eggs either onto the leaves or in the ground are not 

 brought over from the West Indies. There are, therefore, no West Indian Cara- 

 Hdae, Lampyrdae, Staphylinidae and other rhypophagous Clavicorn families and 

 very few West Indian Scarabaeidae and Chrysomelidae to be found in Southern 

 Florida.* This is a most characteristic feature of the semitropical Coleopterous 

 fauna of Florida, strikingly contrasting with the state of affairs in the south- 

 western extremity of North America. I have stated before that along the Texan 

 and New Mexican frontier there Is a perfect intermingling of the North and Central 

 American faunas so that it is impossible to decide whether a miscellaneous col- 

 lection of Coleoptera comes from Western Texas or the adjacent parts of Mexico. 

 A miscellaneous collection, consisting only of about 100 species but made pro- 

 miscuously in semitropical Florida can at a glance be distinguished from a similar 

 collection made in Cuba or any other part of the West Indies. Further, the pecu- 

 liar composition of this fauna at once precludes the assumption that any agencies 

 other than the current of the Gulf stream could have been active in assisting the 

 Immigration from the West Indies, pp. 168-170. 



"Most of the more southern Keys are covered with semitropical forest, i. e. 

 forest covered with composed of West Indian trees, while, as I stated before, the 

 true Floridian fauna and flora are almost entirely absent. These islands are, there- 

 fore, by no means favorable to a stiidy of the relation of semitropical to the true 

 Floridian fauna. However, a stay of a few weeks on the shores of Biscayne Bay 

 fully sufficed to settle this question. Here, as well as on the mainland farther south 

 and the northernmost Keys (Key Largo and Elliott's Key) the Floridian flora 

 largely infringes upon the semitropical forest and reduces the same to smaller 

 or larger island-like patches lying close to the shore or occupying similarly isolated 

 patches on the shore of the Everglades and the few islands in the Everglades. 

 The bulk of the mainland is covered by pine woodsf with an undergrowth com- 



"* The absence of fresh water in the coral region of the keys and the mainland south of Miami 

 River necessitates the absence of uytiscidae ana most other aquatic or semi aquatic families. Even 

 the Everglades and the rivers draining the same at the northern end of Biscayne Bay seem to be al- 

 most destitute of aquatic Coleoptera." 



" t While it is true that the pine of Southern Florida, Pinus Cubensis, is also of West Indian ori- 

 gin. Its distribution in Florida is quite different from the rest of the semitropical flora and its intro- 

 duction is evidently of very ancient date. Its fauna does not differ from that of the Yellow Pine, 

 (P. pahtslris') ." 



