SEA-WATER BREEDERS 227 



the mountain province of Lepanto-Bontoc for the purpose of investigating an 

 epidemic of malarial fever. He fully expected to find that the responsible mos- 

 quito would prove to be a different species, but during his first stay in the 

 province he found what he considered Anopheles ludlowii in the dwellings, 

 while later he also found their larvge breeding in greatest abundance in the 

 rivers and smaller streams of the vicinity. He spent over two weeks in the 

 neighborhood, and made a search for larvae which included the rice fields 

 (flooded at that time of the year), the water tanks near the buildings, and all 

 probable breeding-places. He states that he found no other species of Anopheles. 



It is evident that the observations of Mr. Banks are faulty and inconclusive. 

 From the observations previously cited it is to be seen that Anopheles ludlowii 

 breeds exclusively in saline water. The species which he found at Lepanto- 

 Bontoc and so identified was in all probability Anopheles rossii. However, as 

 this latter species is known to be ineffective as a malaria transmitter, and as other 

 species of Anopheles have a wide distribution in the Philippines, it is obvious 

 that his methods were inadequate. Moreover, it appears that many of the de- 

 terminations were made from larvae and were therefore unreliable, as the 

 Anopheles larvae are very similar and much more difficult to distinguish than 

 the adults. 



Some interesting observations on the existence of Anopheles larvae in sea-water 

 were made by Button in his malaria expedition to the Gambia in 1903 (Liver- 

 pool School of Tropical Medicine, Memoir X). The following account is taken 

 from pages 29 to 30 of his report: 



" A garden tub in which mosquitoes had been breeding was emptied and 

 cleaned, and sea water, taken as the tide was coming in, placed in it, the other 

 tubs in the garden being covered with mosquito netting. In four days afterwards 

 a batch of small Anopheles larvae was discovered in the water, which subsequently 

 hatched out into adult mosquitoes (A. costalis) seven days later. This experi- 

 ment was repeated with the result that first eggs of Anopheles and also Culex 

 appeared in one or two days after the tidal water had been placed in the .tub, 

 and subsequently adult insects hatched out from them. From these experiments 

 it would thus appear that certain kinds of mosquitoes can breed in tidal water if 

 it is not disturbed, and subsequently when the dr}' season had fully set in, I 

 found larvae in suitable tidal pools, namely, as I have already mentioned, in the 

 drains near the sluice gates in which tidal water had soaked in through the 

 gates. In this water, which contained 1038.5 parts of chlorine per 100,000 parts, 

 I found a few larvae of A. costalis and large numbers of Culex halassios. On 

 another occasion, in December, I found these mosquitoes breeding in a small 

 hole from which shells had been taken, close to the edge of the water at the 

 mouth of Oyster Creek. The Culex were subsequently hatched out from this 

 tidal water, but the Anopheles larvge were nearly all infested with a fungus (not 

 identified) which gave them a woolly appearance, and I failed to hatch out any 

 of them. I observed A. costalis breeding in a similar salt-water pool during a 

 period in which neap tides occurred. The tidal water in an arm of the central 

 channel in Box Bar, running from the sluice gates to the cemetery, had become 

 converted into a series of small pools by partial evaporation of the water, though 

 at every tide some water leaks through the sluice gates into this channel, but 

 during this period it was not sufficient to replenish this small branch drain. 

 Anopheles larvae were found in great numbers in these pools. It is interesting 

 16 



