162 Psyche [October 
and this after excluding the Corethrinz. It is not in mere num- 
bers of species that this work displays its merits. It is most 
emphatically a compend of our knowledge—taxonomical, syno- 
nymical, morphological, biological—of a large and important group 
presenting many difficult problems to the solution of which the 
several authors have contributed largely, and at the same time 
most carefully made due acknowledgment of the part played by 
their colleagues. . 
This series of volumes leaves little to be desired along historical, 
biological and economic lines, and since the first two volumes 
appeared in 1912, and were duly reviewed, there is no necessity of 
extended comment in this connection. 
The first part of the taxonomic portion (Volume 3) appeared in 
1915, and is continued in the just issued Volume 4. Obviously 
one could hardly be discussed intelligently without the other. 
The authors have recognized only those genera which could be 
defined by characters found in both sexes, and consequently sub- 
merged some because they were based upon peculiarities exhibited 
by one sex, giving as a reason therefor that not all specimens sub- 
mitted for determination are bred, nor are both sexes always 
represented. This is very frequently the case with other insects. 
It is doubtless more convenient from certain standpoints, and yet 
it is admitted by the authors that genera erected upon characters 
found only in one sex are valid, and the disregard of such genera 
may not be generally accepted. A striking application of this 
method is seen in the inclusion of such different forms as Aédes 
fuscus O.S., now considered a synonym of the European A. cinereus 
Meign., and the large series represented by the salt marsh mos- 
quito (sollicitans), and a number of our common woodland mos- 
quitoes in the same genus. There are marked differences in these 
insects not only in the male palpi, but in the genitalia, and the 
mere fact that there has been reduction in palpal structures in 
several independent series by no means invalidates the use of such 
modifications for generic separation. This is simply a tendency in 
specialization which is closely paralleled in the gall midges where 
we consistently find the same phenomenon, though in both sexes, 
in each of several large tribes and within certain limits the palpal 
reduction indicates the degree of specialization, and in the group 
