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ON THE CHANGES WHICH OCCUR IN CERTAIN CHARACTERS 

 OF ANOPHELES LARVAE IN THE COURSE OF THEIR 

 GROWTH. 



By A. T. Stanton, 



Bacteriologist, Institute for Medical Research, Federated Malay States. 



Introductory. 



It is generally admitted that the ability to determine the species of Anopheles 

 by an examination of their larvae would place a valuable weapon in the hands of 

 the practical sanitarian in tropical countries. In the investigation of an area for 

 the determination of the Anopheles present, it frequently happens that, on account 

 of their habit of concealment by day, adult mosquitos are difficult to find, whereas 

 their breeding places may be located readily. If the larvae are transported to a 

 distance they commonly do not develop further, and so, failing the specific 

 identification of the larvae themselves, valuable information is lost. It is 

 therefore very desirable to know whether, and to what extent, any of the 

 characteristics of such larvae may safely be employed in determining their 

 species. 



Grassi 1 was the first to direct attention to certain characters of Anopheles 

 larvae, notably the form of the clypeal hairs, which he considered to be of value 

 in their specific differentiation. The valuable observations of James 2 and 

 Christophers 3 added greatly to the knowledge of the subject, but later studies in 

 India and elsewhere appeared to show that these characters were not constant in 

 the same species. James and Liston 4 , in the second edition of their monograph 

 on " The Anopheline Mosquitoes of India," give expression to the prevalent 

 belief that " in the larvae of common species some of the characters vary con- 

 siderably and therefore for purposes of identification we are not now inclined to 

 attach very great importance to them." 



In the course of a study of the Anopheles mosquitos of the Malay Peninsula, it 

 was possible by breeding out larvae from the eggs of known species to follow the 

 changes in them at successive ecdyses up to maturity. The results of these 

 observations are set forth in the present paper, and it is believed that they 

 account for the anomalous results obtained by previous workers in this field of 

 research, by showing that the supposed variations of any specific larva are really 

 changes of a constant kind associated with successive phases of development. 

 The difficulty of breeding out larvae from the eggs laid by mosquitos in captivity 

 was not found to be insuperable, and it is considered that the study of such larvae 

 offers certain advantages over the study of the skins cast on their transformation 

 to pupae or of groups of larvae from which a single species subsequently 

 hatches out. 



The larvae of the following species were studied : — A. albirostris, A. sinensis, 

 A. fuliginosus, A. nigrans (—A. karwari), A. umbrosus, A. rossi, and A. ludlowi. 

 As the results were constant and parallel in the case of each species, it will 

 suffice for the present purpose to give an account of only one of these, and I have 

 selected Anopheles albirostris, Theobald, one of the malaria-carrying species of the 

 Malay Peninsula, 



