SUPPLEMENT 



MONOGRAPH OX NORTH AMERICAN DOLICHOPODIDI. 1 



I. General Remarks on the Dolichopodidse of North America. 



That the North American fauna of Dolichopodidse is an ex- 

 ceedingly rich one, is proved by that portion of it upon which I 

 have based the present publication. I am satisfied that this fauna 

 far exceeds the European fauna in the variety of forms and in 

 the number of species. 



I take the following points to be peculiar to this fauna : 1. The 

 apparently rather numerous species of Pelastoneurus; 2. The re- 

 markable abundance of closely allied species of true GymnQpter- 

 nus; 3. The number of species of Chrysotus distinguished by a 

 variety of plastic characters, which is not generally the case in 

 this genus ; 4. The abundance of species of Diaphorns and of 

 forms related to this genus. Our knowledge of the genera occur- 

 ring in Xorth America is too limited, yet, to indicate the absence 

 of some of them as being peculiar to the fauna. 



A very striking circumstance connected with the North Ameri- 

 can fauna of Dolichopodidse is, that precisely in those points 

 which we have just enumerated as peculiar to it, this fauna show- 

 the most remarkable analogy to the remains of the fossil fauna of 

 the same family preserved in amber. In both, there is the same 

 abundance of species of genuine Gymnoptemus, difficnll to dis- 



1 The volume had already gone through the press when the present sup- 

 plement was sent in hy Mr. Loew. It contains descriptions <>f tli>> new 

 species discovered mostly by me duriiiL' the summer 1863. The G 

 /?. murks, prefixed to this Supplement, form an important addition ti 

 preface of this volume (page iii — vi). I >. S. 



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