Notes to Introduction. 
xi 
NOTE B. 
HOW TO EXAMINE AND MOUNT A MOSQUITO. 
The differences between many species of mosquitoes are often 
microscopic, and cannot be detected unless the specimens are 
critically examined under at least a two-third power. In many 
cases dissection is necessary, for the ungues, which can only be 
properly examined when mounted in xylol balsam, often separate 
two closely allied insects. In fact, ordinary museum specimens 
of obscure species are generally valueless in this family of 
Diptera, as I believe they will also prove to be in the case of 
the Cecidomyidae when that family has been properly worked out. 
One great difficulty in describing Culicidae is the varied play 
of colours seen in different lights, especially when examined under 
the microscope and in bright sunlight. Dusky black or brown 
appears violet and purple under the lens, the brown and black 
scales of the legs often assume a bronzy or ochraeeous hue in 
reflected light. The colours of the paler scales also alter at 
death, and under various conditions of death ; white scales in 
the abdominal banding may sometimes be creamy, at others 
dull ochraeeous, and also vary in colour according to the rays 
of light that strike them ; ochraeeous scales, however, never 
fade to white except in very old specimens exposed to sunlight; 
the golden scales often seen on the occiput fade after a time, and 
may become dull golden or even grey in hue. 
A mosquito should be held in all manner of positions before 
it is described or when identifying it; for instance, in the genus 
TJranotaenia a good specific character in some species is to be 
found in the scales at the base of one or more veins of the 
wings, which are often unnoticeable unless the microscope is 
employed and the wings examined in different lights, when 
peculiar form and characteristic colouring may be detected. 
After examining some thousands of specimens I have come to 
the conclusion that the scales form the most, and in fact in some 
groups, the only reliable generic and specific distinctive characters. 
By this means alone I have been able to separate many species 
with superficial resemblances and yet quite specifically distinct. 
