54 
A Monograph of Culicidae. 
in the preceding genera. The head, although large, is propor¬ 
tionately smaller than in Culex. On the thorax are two pointed 
air-tubes, perforated by a very narrow slit; the tail has four 
flap-like processes ; the abdomen has a few tufts of chaetae both 
on the dorsum and venter. At first the colour is white and the 
creature transparent, though of a duller appearance than the 
larva; the pigment cells of the air-sacs of the larva remain and 
show through the skin; later the pupa becomes brownish with 
a broad, dark, double stripe down the mid-dorsal line and with 
two lateral stripes ; the siphons are also dark-coloured and the 
eyes blackish. 
The pupa of this genus can thus be told from those of the 
other genera by the straight abdomen and by the pointed 
air-tubes on the thorax. It. remains upright in the water, often 
for a long time without showing the least movement. Now and 
then it may be seen rising to the surface and sticking its siphons 
out of the water, but never, as in Culex or Anopheles, remaining 
long in that position. It rises and sinks very slowly, thus again 
differing markedly from the pupa of other Culicidae. 
LENGTH OF THE EGG, LARVAL AND PUPAL STAGES 
OF CULICIDAE, 
As in other groups of insects, so with the family Culicidae ; the 
period of egg, larval and pupal life vary in each species. It is 
thus possible only to give a few brief summaries regarding the 
length of the various periods in their life-histories. In the 
various genera there is an uniformity of life-history with the 
exception of Corethra. 
In Culex we find as a generality that the egg stage is very 
short. I have hatched C. pipiens larvae from the egg twenty 
hours after they were laid under natural conditions. Professor 
Howard, writing on Culex pungens in America, says that the 
eggs laid during the night or probably early morning hatched 
out readily in May at 2 o'clock in the afternoon of the same day, 
on warm days. In cooler weather they sometimes remained 
unhatched until the second day. Colonel Giles in his work says 
that Culex eggs take two or three days to incubate, but this is 
longer than usual, I fancy, anyhow in warm weather. 
The larvae live, in the case of Culex pipiens, from t"wo to four 
weeks, moulting their skin three times. The pupae I have kept 
