— 129 — 
M. Herbert Osborn (Ohio State University, Columbus) prend 
la parole : 
Remarks on the Jassid fauna of North America. 
( Résumé.) 
The Jassid fauna of North America is very rich in species and 
^notwithstanding the early work of Say, Fitch and Uhler and the 
more recent contributions of Van Duzee, Gillette, Ball, 
Baker and others much remains to be done. 
This fauna shows a close relationship with the European espe¬ 
cially in the family Jassidæ proper and with the Central and South 
American more particularly in the Tettigonidæ. In such large 
genera as Deltocephalus, Thamnotettix and Phlepsia the species 
common to Europe and America are few, and we may assume the 
evolution of maSy of the American species within this geographical 
area. Of the factors operating to produce such evolutions may be 
mentioned the adaptations to climatic conditions and to food plants. 
Many examples show now distinct limitation to humid or arid 
regions and to one or but few hort plants. Many examples may be 
cited to bear out this statement and also to show extremes of 
adaptation evidently acquired within the restricted range of the 
species. (Vol II, flémoires, p. 235.) 
Le R. P. Wasmann (Luxembourg) bemerkt, dass auch bei 
den Ameisen, z. B. innerhalb der Gattung Formica , ähnliche 
Differenzen zwischen den Formen von Nord-Amerika und Europa 
sich zeigen, die zum Teil auf gemeinschaftliche Abstammung, zum 
Teil auf parallele Entwicklung zurückzuführen sind. 
9 
