ECOLOGY OF ISLE ROYALE, 177 



eoptera in the whole world come from Mexico, they have no bearing on this part 

 of my inquiry; for they come from parts of Mexico which are in direct com- 

 munication with another stirps, the rich Coleopterous fauna of Brazil and Vene- 

 auela; and the vast multitude of small European-looking species which occur 

 on the high lands and western side is quite suflBcient for my purpose. The col- 

 lections made by Truqui in Mexico show this thoroughly microtypal character 

 in a very marked way, Staphylinidous genera, such as Falagria, Homalota, &c., 

 abounding. Mexico, being a sort of halfway house between Europe and Australia, 

 might be expected to contain species both from the north and the south which 

 have got thus far. Eleodes is an instance of this from the north, Philonthus 

 another; both reach as far as Chili, but not into Australia. Zopherus, on the 

 other hand, is an instance of a species which occurs in Australia, and runs up 

 into Mexico, where it is in strength, and goes even a little further. Mexico may, 

 indeed, have been its starting-point, but the connexions and relations of it and 

 the allied genus Nosodendron decidedly indicate a separation between the eastern 

 and western type of both; and the western type extends into Australia and New 

 Caledonia." p. 38. 



ScTiwarz, E. A. 1888. pp. 166-167, 168-170, 171-172. "After a study of this 

 peculiar fauna of Key West which I also found on many other localities farther 

 north and which constitutes the semitropical fauna of Florida, I have come to 

 the conclusion that it is entirely of West Indian origin, and that the region I shall 

 hereafter circumscribe as Semitropical Florida does not contain any endemic 

 forms. In other words, the distinctive fauna of Southern Florida is a permanent 

 colony of West Indian forms, much more numerous in species than it has 

 hitherto been supposed; the number in Coleoptera alone amounting, accord- 

 ing to a very low estimate, based upon my collection, to at least 300 species not 

 yet in our catalogues, pp. 166-167. 



"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 characters of both regions, but 

 is more nearly allied to the latter than to the 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 the 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 

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

 On the mainland we find between California 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 fam- 

 ilies participate in this intermingling. It is thus impossible to decide whether a 

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

 'Biologia Centrali-Americana' as coming from Sonora, Mex. pp. 167-168. 



"In looking for the original home of this colony of West Indian insects and 

 plants we have been hitherto too much accustomed to consider the Island of Cuba 

 as the only place from which this immigration has taken place. In the task of 

 determining my South Floridian Coleoptera 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 



*See Dr. Q. H. Horn's "Notes on the 'Biologia Centrali-Americana,' " Trans. Amer Ent Soc 

 Vol. XIII, Month. Proc, p. VII. 



