SUPPLEMENT 



TO THE 



MONOGRAPH ON NORTH AMERICAN DOLICHOPODIM.' 



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 Gymnopter- 

 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 Diaphorus 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 shows 

 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 Gymnovternus, difficult to clis- 



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

 plement was sent in by Mr. Loew. It contains descriptions of the new 

 species discovered mostly by me during the summer 1863. The General 

 Remarks, prefixed to this Supplement, form an important addition to the 

 preface of this volume (page iii — vi). 0. S. 



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