258 
ORIGIN OF LIFE IN AMERICA 
Guatemala during a residence there of several years, states 
that the mite-fauna of Central America is composed of the 
same genera as that of middle Europe. In some cases even 
the species are identical. It is true that most of these genera 
also inhabit Asia, though Linopodes, Haplophora, Nicoletiella 
and Uropoda have not yet been recorded from that continent. 
As some of these are known from the Oligocene Baltic amber 
deposits, it is probable that the genera date back to at least 
early Tertiary times. 
Of the nearly related spiders and harvestmen, Mr. Pickard - 
Cambridge * remarks, that while the majority of the Central 
American species are peculiar to the Nearctic and Neo¬ 
tropical regions, the genera are in many cases identical with 
those of the Mediterranean region, India, Australia or Africa. 
There are not now in existence any land connections, he con¬ 
cludes, which an arachnidal fauna could take advantage of 
in order to pass from Africa, Australia or Europe to North 
or South America, and we can only suggest that at some 
period or other these now widely separated regions must 
have been linked together by land which has long since dis¬ 
appeared. 
The various groups of Central American insects are as yet 
far from well known, and their relationships with the insects 
of other regions have been but imperfectly determined, not¬ 
withstanding the fact that Messrs. Salvin and Godman have 
published a series of fine volumes about them. The consensus 
of opinion of the writers, who have contributed to the 
“ Biologia Centrali-Americana,” is that Central America 
is essentially a part of South America. The purely North 
American forms are few in number, their southern limit being 
as a rule in Mexico. This verdict agrees also with that of 
Dr. Calvert,f who in his recent researches on the dragon¬ 
flies (Odonata) of Mexico and Central America, comes to the 
conclusion that in the endemic as well as in the non-endemic 
species, the South American element is much the strongest. 
Before concluding this chapter, I might again emphasize 
the fact that the occurrences of northern genera and species 
in Central America are almost all discontinuous. I need only 
* Pickard-Cambridge, O., “Araneidaof Central America.” 
f Calvert, P. P., “ Odonate Fauna of Central America,” p. 467. 
