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THE NATURE AND FUNCTION OF THE CAUDAL TUFTS OF MALAYAN 



ANOPHELINE LARVAE. 



By W. A. Lamborn, 

 Malaria Bureau, Federated Malav States. 



It has been found difficult to understand how such a fragile creature as an 

 Anopheline larva could withstand the force of a strong current of water. In the 

 following article it is proposed to explain the phenomenon on anatomical grounds. 



The writer's previous experiences in Central Africa, where the seasons are far more 

 definite than in the Federated Malay States, had shown that in the dry period, when 

 there is often an entire absence of other possible breeding-places, the larvae of 

 Anophelines are to be found in among the vegetation fringing the banks of the great 

 rivers ; hence, for instance, the notoriety as regards malaria of the whole extent of 

 the Shire valley, in N3/asaland. 



It was decided in June 1920 to make a tentative examination for larvae of the 

 Klang River and its affluents in the vicinity of Kuala Lumpur, F.M.S., though there 

 was not at that time any great expectation of being successful in the search. It is 

 true that Dr. Hacker had in 1918 demonstrated the presence there of the larvae of 

 A. maciilatus, Theo., and A. aconitus, Don. ; but apart from the numerous breeding- 

 places afforded elsewhere, swamps, grassy pools, muddy pools, drains, and excavations 

 of various sorts, the heavy rains at frequent intervals during the previous three months 

 had ensured the flow of a volume of water so enormous and a current so swift as to 

 make it appear impossible that an object so fragile as a mosquito larva could maintain 

 itself therein. 



A few Anopheline larvae — A. subpictits, Grassi, var. vagtts, Don. (.4. rossi, Giles, 

 var. indefmitus, Ludl.), .4. barbirostris, Wulp., A. hyrcanus. Pall. (.4. sinensis, Wied.), 

 -4. aconitus, Don., A. nianilatus, Theo., A. leucosphyrus, Don.- — were discovered, and 

 even with the river running strongly, could constantl}' be found in among the stems of 

 the reeds and long grass at its sides. At no time were they numerous, and careful and 

 diligent search was necessary to obtain them in a rapid current. The significance of 

 their presence would appear to lie, not in their numbers, but rather in their ability' 

 to maintain themselves in such a situation, from which in due covnse the adults can 

 diffuse themselves over the surrounding country, selecting at will, possibly at another 

 season, breeding-places more auspicious to the welfare of their larvae. 



The question which then arose was : How do the larvae manage to maintain them- 

 selves without being swept away ? For not only in the river, but in other running 

 water are the larvae of certain species constantly to be found. 



A . maculatus larvae, for instance, can invariably be found in a grassy drain beside 

 a railway embankment just outside the town, in which a considerable volume of water 

 is usually flowing. A few A . karwari larvae were once found by the writer at Sungei 

 Besi, eight miles south of Kuala Lumpur, apparently quite at ease at the side of a 

 pot-hole through which the water was literally rushing from a higher level. The 

 larvae of A. aitkeni, James, almost invariably favour jungle streams. 



Some observations made in this connection so long ago as 1911 by Dr. Malcolm 

 Watson, and recorded in his book " The Prevention of Malaria in the Federated Malay 

 States " (p. 105), are of no small interest. Dr. Watson expresses the opinion that the 

 ova of A . maculatus {wilmori) are laid in the shallowest possible water, usually at the 

 head of a ravine, and the paragraph discussing further the distribution of the larvae 

 is as follows : — 



" From these springs the larvae are carried down by the streams, but they cannot 

 be entirely washed out even by the strongest currents or rains. I have found them in 



