REPORT OF THE MALARIA EXPEDITION. 
19 
(i.) A. ioitcilh was found all over the low-l\ ing areas examined b\- us. Tliat is, the larv;e 
which yielded this species were found in all these areas ; though it wa-, mucli more difficult to 
obtain the adults. The adults were most numerous in the Wilberforce Barracks (600 feet) ; but 
were also obtained in other parts of the town, as far east as the subui'b of Kiss^'. No atiidts were 
ever seen in the barracks and officers' quarters on Tower Hill (400 feet) ; although there were 
numerous breeding-pools onh' 500 Aards to windward. None were found in the barracks on 
Mount Aureole (900 feet) ; although pools la\- all round the base of the hill. 
(2.) A. funcstui was restricted entirelv to the eastern part of the town ; we never found a 
larva nor an adult of this species west of Government House. Not one was seen in Wilberforce 
Barracks, where A. costalh was so common. Individuals were caught in a house in the town 
where some cases of fever had occurred ; at Leicester, a v illage high among the hills ; and at 
some other points. The larva; were common in pools in the eastern quarters, at Kissy, and other 
spots. 
It is curious that while onl)' the large species occurred at Wilberforce, it was almoit 
entirelv the small species wliich was found at Kissy. 
15. Bionomics of Anopheles Larvae. We made the following observations : 
(i.) ^^^--i. These are like tlK)se ()f ////^/)/;/'/« ()bserved in India. They appear 
to be laid singl\' on water ; but cohere by their ends, forming typical triangular patterns ; and also 
adhere to floating objects, the sides of the vessel, etc. We observed no facts indicating that they 
are ever laid on solid surfaces. In vitro the\- take about 24 hour^ to hatch ; but the period is 
probably much shorter in puddles. 
(2.) Duration of larval stage- This depends on temperature and amount ot food. Under 
natural conditions it may probabh be onl\- three or four da\ s ; but under unfavourable conditi<)n> 
(cold, overcrowding, absence of f.tod) it ma\- certainh' extend to weeks. I here are reasons for 
thinking that development is much hastened b\ bright weather, in order to enable the imag<j to 
hatch out before desiccation (jf the containing puddle. 
(3.) Food. The larv:e were frequentiv watched floating on the surface and feeding on 
filaments of water-weed -amongst which the\' often entangle themselves. On dissection, the 
intestine was found crammed with these filaments. It was observed that in vitro the larv:e 
scarcely grow in size unless the)' are given large quantities of water-weed which they dispose of 
very rapidl)-. On the other hand, larva- were often caught in puddles in which no green 
vegetation could be seen. The\ ma)- eat other food, but it wouUl Ncem as if water-weeds 
constitute their favourite diet. It was also noted that the\' obtain shelter among these weeds from 
the ciu'rent rumn'ng through the pools during or after rain. 
(4.) E>ic)iiirs.— observations couKl be made under this head ; but we often fomid nian\' 
frogs and tadpoles in the breeding-pools, apparently living at peace with the larvct. 
(5.) Eff'ect^ of dfsiccation. — During most of our stay in Freetown heav)' showers fell several 
OiiL- of US kept Ciilcx l.irva- .illvi- tor ci iiiiint]v; In .1 bnUk- in the col. I wimiIrt in In.li.i. 
