REPORT OF THE MALARIA EXPEDITION. 25 
may continue to exist in sucli pools as do remain, the insects multiplying enormously after the first 
showers ; or (2) that the eggs may lie dormant in mud ; or (3) that the adults may "hibernate," 
or at least live on without feeding on blood at all, and consequently laying no eggs. We cannot 
pretend to give an answer to this question. In Italy it appears that the adults hibernate through 
the winter. One of us made an observation tending to show that the eggs can withstand 
desiccation for several months ; but this requires confirmation. The subject appears to be of great 
importance in connection with the prevention of gnat-fever [paragraph 28']. 
(2.) Other subjecti.—-\t is necessary also to examine how far Anopheles do or do not exist 
apart from human dwellings ; whether they can breed in other collections of water than those 
mentioned above, as, for instance, in rain-water collected in leaves ; whether they really have any 
connection with rank vegetation ; how far they can spread from tiieir breeding pools, liow far they 
feed on animals, and so on. 
We must again emphasize the tact tliat our remarks as to the bionomics of tliese insects are 
drawn only from our experiences within a limited area of Freetown \_Map II.] in the months of 
August and September. We can make no statements regarding their habits, or the habits of other 
species of Anopheles^ outside tiiis limited area, or at other seasons. 
18. Source of the Wilberforce Anopheles. — As an instance of the difficulties which 
may be met with, we may mention that, in spite of repeated efforts, we never succeeded in 
finding the source of the A. costalis which were so prevalent in the barracks at Wilberforce. These 
barracks are situated on a ridge 600 feet above sea level, and are surroiuided by native houses and 
gardens, and by much rank vegetation. The ground slopes on either side down to the plains. 
Far below to the west (that is, to windward during the rains) there are a marsh and a mangrove 
swamp. 
We searched in vain every spot likely to harbour Anopheles larvas ; and even examined the 
distant marsh and mangrove swamp without positive results. After our departure Dr. Fielding- 
Ould and Captain Smith, r.a.m.c, continued the search — equally in vain, except that they found 
larvae in pools 1,500 yards away {^Addendum II.]. 
It was often observed, however, that the Anopheles frequented two or three of the barracks 
in preference to the other buildings, and that these barracks were at the end of the block of houses. 
At the same time, the insects were common in the houses of the officers, who lived at that time in 
the village. These facts suggest that their source existed near these buildings, and not at any 
great distance, and that it was probably overlooked owing to the thick vegetation present. It 
seems very unlikely that such numbers of the insects could come from breeding pools in the 
. marshes which lie thousands of yards away in the plain below. 
The fact that so many of them were caught for examination seemed materially to affect 
their numbers ; but we noted that newly-arrived insects invaded the barracks on one, if not more, 
occasions. 
D 
