322 On the Diptera of the Amber-fauna. 
will be more difficult, however, to explain how JIlythea sprlota, 
Dichela caudata and D. brevicauda, Ochthera Mantis, etc., should 
have crossed the sea. The importation of some species, as, for 
instance, of the beautiful Psilopus albinotatus, discovered by me 
in Rhodus, seems almost inexplicable, and still this species is 
perfectly identical with the North American P. pallens. That 
nevertheless occurrences of this kind, owing to the large numr 
; We have to 
conclude then, for the present, that the importation of species 
through the agency of frequent intercourse, does not afford & 
sufficient explanation of the large number of species common to 
men 
ones.—Still better known is the influence which certain we 
exercise on the coloring of all the species occurring there; oo 
is, for instance, in a very striking degree, the case with Icel 
‘A collection from that country, at a cursory view, seems gee 
tain many new species, but upon closer examination, these 
