INTRODUCTION. Vv 
make many fresh genera, viz. in the Lampyride and Cleride, of the former five genera 
out of sixteen occur in the Nearctic region also, but twelve at least occur and are well 
represented by species in South America; of the latter there are 25 genera (omitting 
Necrobia which is universal); of these, four occur in the Nearctic, seven in the Nearctic 
and Tropical South American regions, and five are common to Central and South 
America. 
These facts show the preponderance of relationship between our fauna and that of 
Tropical South America over any community it possesses with that of America north 
of Mexico. 
But this conclusion is rendered even more apparent if we consider the relative | 
numbers of species in some of the larger genera. Calopteron is a genus of the Lycide 
eminently typical of Tropical South America, where 70 species at least are known to 
exist. Now, north of Mexico, only three species are known, but in Central America we 
have 42 species. To give another instance, from the Telephoride, Chauliognathus is 
represented in America north of Mexico by 8 species, in Central America by 45, in 
South America by 28 species; the latter figure by no means representing the actual 
number, as the species of that country have not been much worked at, while the North- 
American are nearly certainly known. On the other hand Podaérus, a Nearctic genus, 
especially abundant in North America, where it has 32 species, is barely represented by 
a solitary species in Northern Mexico and does not pass further south. 
More striking, however, is the marked peculiarity of the Central and South American 
genera as compared with the faunas of other parts of the globe. If it were true that 
similar conditions would produce similar forms, how is it that the specialized genera of os 
the Neotropical region are so dissimilar to those of the Athiopian and Indo-Malayan ? 
Of the few genera common to our district and to the Palearctic or Tropical regions of 
the Old World, I do not hesitate to affirm that there is not one which is not of the 
rank of feebly differentiated forms, or persistent forms of an earlier stage of development. 
The apparent exceptions in the Lycide of Lycus and Lycostomus, in the Telephoride 
of Silis, in the Ptinidee of Ptinus, and in the Cioide of Xylographus, being due to the 
imperfectly characterized condition of those genera; while the total absence of such 
widely distributed and well-marked forms as Erosand Calochromus, Luciola, Telephorus 
(proper), Malachius, Dasytes (proper), Henicopus, Melyris, Cylidrus, Opilo, and Trichodes . 
cannot be explained by any intrinsic dissimilarity in the conditions, which certainly 
do not differ more than they do in the wide areas over which these genera are dispersed, 
