THOMPSON: ANATOMY OF MOSQUITO. 
147 
it must be constantly controlled and supplemented by sections. 
Knowledge of the structures within the head of the insect on the 
other hand, has to be derived almost wholly from sections. Recon- 
struction proved of slight value. I used serial sections cut in the 
three planes usually employed and depended on careful study of 
4 
these, adding to and controlling the interpretations by study of dis¬ 
sections and of material cleared with caustic. Excellent thick sec¬ 
tions— 30 fx or over — for control and demonstration were prepared 
by killing in Flemming’s fluid and allowing the specimens to blacken 
somewhat. Material treated thus may be imbedded in paraffin, sec¬ 
tioned, and the sections mounted without staining. The discolora¬ 
tion produced by the killing fluid gives sufficient character to the 
structures. 
With the larva of the mosquito, study of the living animal or of 
fresh dissections is of paramount importance. Sections of the head 
especially are not readily interpretable taken alone. Fortunately 
for research, the wriggler of Culex has a large, transparent head, so 
that the contained structures can easily be made out in the living- 
animal or in whole mounts of the head. In the light of knowledge 
obtained in this way, sections become interpretable and through 
these in turn we are enabled to understand sections of the Ano¬ 
pheles wriggler, where the head is small and opaque. An excellent 
method for mounting the whole head is to stain with picro-carmine 
and then clear through Weigert’s fluid. Fine preparations may 
also be obtained by staining with haematoxylin, but this method 
is slower and less uniformly successful than the picro-carmine stain. 
The pupa stage can only be studied from serial sections and to 
work to best advantage a series of specimens the ages of which are 
approximately known, is needed. Such a series was obtained for 
Culex by segregating mature larvae in a dish and each hour remov¬ 
ing all pupae to separate containers, in which they could be reared 
for any desired number of hours. A very complete series ought to 
be obtained. In the summer our species of Culex spend from 48 to 
70 hours as pupae, and I did not find that a set of specimens repre¬ 
senting in ages nearly every hour up to the thirtieth of pupal life 
and then more distant intervals, was too extensive. 
