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perish in the unsuitable pools, or that the adults generally return to the same pools 
in order to lay their eggs. It seems likely that the adults generally lay their eggs in 
the pools in which they themselves were bred, and that the insects thus learn by 
experience the places most suitable for them. 
(7) Detection.—It is easy to overlook Anopheles larvee unless they are searched for 
in a bright light. 
(8) Pupe.—The pup of Anopheles seem to be smaller than those of the com- 
moner species of Culex. They require about forty-eight hours to reach maturity in 
vitro; perhaps less in natural conditions. 
16. BIONOMICS OF ADULT ANOPHELES. 
(1) Hatching.—The adults generally hatch out in the evening; but their exit seems 
often to depend on the meteorological conditions of the moment, and appears to be 
delayed by rainy and windy weather. 
(2) Food.—They can easily be kept alive in glass cages, test tubes, bottles, etc. 
We kept some in this manner for a fortnight, and could doubtless have kept them 
longer if we had wished to do so. We are able to confirm Bancroft’s statement (18) 
that gnats feed on bananas; but they seem to prefer the fresh fruit. During the day 
the insects remained at rest on the walls of the cage, but in the evening began to 
fly about and to walk over the fruit, plunging their proboscis into it in many places, 
so that the banana was sometimes covered with gnats, both male and female. They 
also drink water frequently, and each can often be seen to be distended with the 
fluid. Raw meat was offered to them, but they could not be observed to touch 
it. Earth placed at the bottom of the cage seems to be suitable for them. 
According to the accounts of the soldiers at Wilberforce, they bite almost entirely 
in the evening and night, but have been known to feed on men during the day. 
They can certainly be fed on men artificially during the daytime, simply by placing 
them in test tubes and then applying the mouth of the tube to the skin. The stom- 
ach can be observed to become distended in from one to two minutes or more; after 
which the insect continues to suck, but commences to evacuate by the anus serum 
containing a small percentage of red corpuscles. Culex voids only a clear fluid under 
the same circumstances. The insects sometimes continue sucking like leeches for 
five or ten minutes, voiding blood all the while; but at other times soon withdraw 
the proboscis and then try another spot. It was noted, however, that Anopheles 
fed in this manner, even after they had remained sucking for five or ten minutes, 
never showed any great distension of the abdomen; while the contents of the stom- 
ach still remained for some time transparent and red as seen through the scales of the 
living insect. Moreover, in these cases the meal was generally digested or voided 
within about twenty-four hours. 
On the other hand, Anopheles which had fed themselves under natural conditions 
generally presented a very different appearance. They were enormously distended; 
while the contents of the stomach were thick, opaque, and black, and sometimes did 
not disappear for three days. The only inference is that, under natural conditions, 
the insects which can manage to do so gorge themselves over and over again during 
the night—probably from the same subject. 
(3) Propagation.—We also observed that while naturally fed gnats invariably laid 
eggs after two or three days, those which had been bred from the larvee in captivity, 
and had then been isolated and fed in test tubes, never did so, although before being 
isolated they had long been in company with males. The inference is that fertiliza- 
tion takes place only after the female has been fed. 
We noted also that in a cage where many male and female gnats, Culex and Ano- 
pheles, were kept together for weeks eggs were never laid, although the insects were 
fed as described on bananas, and the cage contained water for them to lay their eggs 
in. It seems, then, that a meal of blood is necessary before fertilization. 
