INSECTA. 
529. 
DIPTERA. 
A. Separate Publications. 
Loew^ H. Monographs of the Diptera of North America. 
Part II. Edited by R. Osten-Sacken. Smithsonian Mis- 
cellaneous Collections, 171. 8vo, pp. xi & 360, with 5 
plates. Washington, 1864. 
In this Avork Dr. Loew has not only furnished us with a com- 
plete monograph of the American Species of the difficult family 
of the Dolichopodidce y but has also characterized the whole of 
the known genera. The genera and species are described in 
considerable detail, and their investigation is greatly facilitated 
by carefully prepared tables. Including the Rhagoneurus 
( — Rhageneura,Ronl\.), of which a modified character is given 
by the author in his supplement, the total number of genera 
admitted is 44, of which 29 are represented in North America. 
The total number of well-ascertained North- American species 
described by Loew is 175 ; but he includes in this list some from 
the tropical parts of the western continent, and even from the 
West Indies and Venezuela. Of the American species 41 are 
described as new. Loew has frequently found the descriptions 
given by former writers quite inapplicable to any species with 
which he is acquainted ; these descriptions are quoted at length 
under the genera to which the species described appear to 
belong, so that his monograph may be said to include the whole 
body of literature on the Dolichopodidm of North America. The 
plates appended to the volume contain representations of illus- 
trative species of each of the 44 genera admitted by' the author, 
showing the general form of the animals and the more important 
details of their structure. 
Loew remarks [op. cit. pp. 321 & 322) that the North American 
fauna appears to be particularly rich in Dolichopodidse. He 
indicates as peculiarities in it the number of species of Pelas^ 
toneuruSy the number of closely allied species of Gymnopternmy 
the number of species of Chrysotus distinguished by plastic cha- 
racters, and the abundance of species of Diaphorus and allied 
forms, and remarks on the singular coincidence in these respects 
between the North- American fauna and that of which the remains 
have come down to us preserved in amber. 
As regards the geographical distribution of the Dolichopodidse 
the author^s investigation of the North- American species leads him 
to the following results. The North- American fauna closely 
approaches the European and North-Asiatic in the species of 
liygroceleuthuSy DolichopuSy TachytrechuSy CampsicnemuSy Scellus, 
HydrophoruSy LiancaluSy Chrysoiimus, and XanihochloruSy whilst 
its relation to the South American is shown by the species of 
1864. [voL. I.] 2 M 
