-i67- 



contain anv endemic forms. In other words, the ilistinctive fauna of 

 Soutlicni l'"iorida is a permanent colony of West Indian forr.y , much 

 more numerous m species than it has hitherto been supposed ; the 

 number in C'o]eoj)tera alone amounting, according to a very low estimate, 

 based upon my collection, to at least 300 species not yet in our cata- 

 logues. In describing sjiecies from Southern Florida the point I have 

 just mentioned has l)een t 'O much overlooked, the result being that 

 manv of these species prove to liaxe been jireviously described from the 

 West Indies. 



Tliis conclusion which of course cannot be fully proven before we 

 have acquired a more complete knowledge of the West Indian faima, 

 but which is fully sustained by the peculiar composition and mode of 

 occurrence of the semitropical insect fauna of Florida, forms the starting 

 point of the following remarks. 



Before entering on a discussion of the character and extent of this 

 West Indian colony in Florida it seems worth while and instructive to 

 give a glance at the south-western extremity of North America where 

 our fauna comes also in contact with a semitropical fauna. The great 

 faunal regions known as Nearctic and Neotropical are connected or 

 divided by the Central American fauna which from the nature of the 

 conditions participates in the ciiaracters of both regions, but is more 

 nearly allied to the latter than to tlie former. It is again divided into 

 the fauna of the Central American continent and the Insular fauna of 

 Central America, more commonly called the West Indian fauna ; these 

 two faunal regions being related to each other in the same degree as is 

 the fauna of our Atlantic slope to that of die Pacific slope. At the zone 

 of contact between the North American fauna and that of Mexico the 

 conditions are as follows : The ocean current along the Pacific coast of 

 North America runs from north to south, thus facilitating the spread of 

 more northern species southward. It loses its force and disappears 

 before reaching southern California and thus the North American launa 

 along the coast does not come into contact with that of the Mexican 

 coast. On the mainland we find between CaUfornia and the largest 

 portion of Arizona on the one side and Mexico on the other, a broad 

 tract of the most barren and sterile country * which proves to be a most 

 effectual barrier between the two faunal regions. Farther east, and 

 more especially along the Rio Grande, a complete intermingling of the 

 two faunas takes place in such a way that species of all families partici- 

 pate in this intermingling. It it thus impossible to decide whether a 

 collection of insects comes from Texas or the State of Tamaulipas, or 



* See Dr. G. H. Horn's "Notes on the ' Biulot^ia Centrali-Americana,' " Trans. 

 Anier. Ent. Soc, Vol. XIII, Month. Proc, p. VII. 



