1054 The American Naturalist. [December, 
1878, while very important, include only one work which describes 
new North American species—Vol. I of the Diptera in Biologia Cen- 
trali-Americana. 
In 1879 appeared the first paper of S. W. Williston, inaugurating a 
new American period, which has continued to the present time. After 
a few years D. W. Coquillet began to publish, followed by C. H. Tyler 
Townsend, and he by others, until the number of those who publish 
occasional papers is now ten or more. 
The recent appearance of Dr. Williston’s Manual of North Ameri- 
can Diptera’ gives reason to hope that the immediate future will greatly 
increase the number of workers in this order, so that we will be justi- 
fied in counting a new era from 1896. It is now possible to determine 
the genera of nearly all the flies of North America, including the West 
Indies, with no other work of reference than this volume. More than 
Cresson’s Synopsis does for the Hymenoptera, or Leconte and Harris’ 
volume does for the Coleoptera, this book does for the Diptera, because 
it includes the territory southward to the Isthmus of Panama. Only 
the Tachinidee and Dexiide are not tabulated and analytically reduced 
to genera, and in this confused mass a bibliographical generic list is 
given, extending to 272 numbers. 
While the book purports to be a second edition of the small one pub- 
lished by the same author in 1888, it is practically a new work, having 
been entirely rewritten, greatly enlarged, and extended to include the 
entire order with the exception noted. The bibliography since 1878 is 
given, and all genera not found in Osten Sacken’s catalogue have refer- 
ences (in the index) to their descriptions. 
The external anatomy of Diptera is very fully treated. Dr. J. B. 
Smith’s interpretation of the mouth parts is given in addition to the 
usual one, the author not assuming to decide between them. Professor 
J. H. Comstock’s system of wing nomenclature, as used in his manual, 
is given a place for comparison, but is not used in the work “ for two 
reasons: First, that it has not yet been fully crystallized into perma- 
nent shape; second, because nearly all the existing literature has the 
nomenclature here employed, and to use a new one would largely de- 
feat the object of the work in the hands of the beginner.” Baron 
Osten Sacken’s system of bristle-naming or chetotaxy is quite fully set 
forth. Each family table is preceded by a full exposition of the family 
characters and a description of the larva, its mode of life, food, ete. 
(where known). ; 
2 Manual of North American Diptera. By Samuel W. Williston, M. D., Ph. D- 
. LIV, 167. James T. — New Haven, Conn., 297 Crown St. Paper, 
$2.00; cloth, $2.25. - 
