184 MOSQUITOES OF NORTH AMERICA 
the species of Aédes and Anopheles. In those forms in which the abdomen is 
compressed or wedge-shaped, it is often very difficult to get the parts into posi- 
tion for a dorsal view. It is then necessary to press the tip of the abdomen with 
forceps until the parts lie flat, and this is best done while the specimen is in the 
oil of cloves. Sometimes the end pieces of the claspers are folded under, and 
then it requires careful manipulation to bring them into view without injury. 
In certain cases, where the genitalia are very compact, and in others where they 
are very complicated, it becomes necessary to break them up in order that the 
details may be brought into view. This must be done carefully under a dis- 
secting microscope or a good lens, and requires skill and practice. 
The slides should be numbered and the data entered in a book. The mosquito 
from which the genitalia were taken should receive a pin-label referring to the 
number which has been given to the slide. 
Whole adults or portions of them or entire larve which it is wished to mount 
can be treated with caustic potash in the manner above described. 
COLLECTING LARVE. 
All mosquito larve are aquatic, and all sorts of water should be examined to 
collect them. In general, lakes, ponds and streams are not suitable breeding- 
places, for these larger bodies of water contain insufficient nourishment for 
the larvee, and generally do contain fish, which would devour any larve that hap- 
pened to appear. It is exceptional for mosquito larve to be found in large, or 
running bodies of water, though there are such exceptions. Anopheles larve not 
infrequently breed along the margins of swiftly running streams, and large 
ponds may harbor Culex larve in their grassy edges. Mansonia larve live in the 
mud at the bottoms of the sedgy swamps, attached by their air-tubes to the vas- 
cular roots of the aquatic vegetation. In the tropics, almost any water may con- 
tain larve. The collector will, however, find the best results in small stagnant 
collections of water, particularly those of a transient character. The different 
genera will be found to occur in different situations. For example, Aédes, with 
the Psorophora that prey upon them, in temporary ground pools, some species in 
tree-holes ; Culex, with the predaceous Lutzia, in permanent or semipermanent 
ground pools; a few species in tree-holes; Bancroftia, with their enemy Mega- 
rhinus, in tree-holes, some species in bromeliaceous plants; Deinocerites and 
allies in crab-holes ; all the sabethids in water in the leaves or flower-sheaths of 
plants, some species in tree-holes, etc. The sabethid larvee, in the tropics, re- 
quire especially careful search, as they occur in such peculiar locations, while 
every different plant harboring them will be found to have its own fauna both 
of Wyeomyia, etc., and the predaceous Lesticocampa and others. This fauna is 
especially characteristic of the tropics, where many plants are water-bearing ; 
but in our temperate region only a single sabethid occurs. It has, however, the 
normal habits of its tribe, living in the water in the leaves of the pitcher-plant, 
Sarracenia purpurea, the only water-bearing plant of temperate distribution. 
The season of the year is an important factor in the occurrence of species, 
rains being essential to the development of perhaps the majority of larvee. Espe- 
