vl INTRODUCTION. 
but rather by the isolation from these other areas, contact with which is only effected 
through the northern portion of the globe. 
One further fact is worthy of notice, viz. that, to whatever cause it may be due, 
where a genus is common to Central or South America and other distant parts of the 
World, it is also the case that it is represented by a species also identical or nearly so 
in both districts. In this case its presence must either be due to transmission recently, 
through artificial means, or to the conditions having long remained practically similar 
under which it exists in places so far apart. The genera Plateros, Lycostomus, Meli-. 
tomma, Atractocerus, Necrobia, Apate, Dinoderus, and Cis, all afford examples of this. 
remarkable truth. Cylidrus, indeed, occurs in Brazil, but only in a species known to 
inhabit Madagascar and the eastern coast of Africa with very slight modification. 
Atractocerus, of which the distribution is remarkable, is represented by a species hardly 
differing from an African one. Dinoderus is a North American. genus but with one 
cosmopolitan species. C%s has one species with difficulty to be distinguished from the 
common C. boleti of Europe. | . 
A few words as to the materials which have been at my disposal may be useful. It 
is probable that (thanks to the liberality of the Editors, who have spared no trouble or 
expense to obtain for the purpose of the work all the large collections that were 
available) such a mass of specimens in this group were never brought together before. 
These were very largely increased by their own collectors, especially by Mr. Champion, 
who paid a very great deal of attention to this group, more especially to the Lycide, 
Lampyride, and Cleridee—all numerous in species and individuals in the humid forest- 
regions of Central America—and sent home large and beautiful series often amounting 
to 100 specimens of a species. Roughly speaking I do not think that less than 10,000 
specimens have passed through my hands, and been separately examined during the 
progress of the volume. | 
The northern portion of Mexico (including the large State of Yucatan), and Costa 
Rica, still remain, comparatively speaking, unexplored. 
H.S. G. 
May 1886. 
