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APPENDIX A. 



The Study of Mosquito Larvce. 

 By Dr. W. M. Graham. 



To render the study o£ Mosquitoes practically useful to the sanitary officer, 

 it should be made possible upon catching an adult mosquito anywhere, to 

 say : this mosquito was bred in a w^ater-butt, puddle, bamboo, empty tin, etc. 

 It would thus be only necessary to find and destroy the breeding-place. 



With the furtherance of this object in view, an attempt was made to 

 collect all the larvae of the locality, to rear them, to identify each willi 

 its imago, and to produce a photograph of each larva and pupa for future 

 reference. 



Difficulties were met with in rearing some species : either the larva died, 

 or the eggs never hatched, but probably greater experience would enable 

 artificial conditions to be sufficiently improved to allow of the rearing of 

 these fastidious species. 



The following were the methods adopted : — All local collections of 

 water were searched for larvae. A white enamelled steel soup-ladle, supple- 

 mented by a smaller spoon for narrow places, was found most suitable for 

 catching larvae. 



The larvae when caught were placed in glass tubes and subsequently 

 carefully sorted. Those belonging to separate species w-ere placed in 

 separate wide-mouthed glass jars half filled with the water of the pool in which 

 the larvae had been found, a layer of the mud having first been placed upon 

 the bottom of the jar. The top of the jar was covered with wire gauze, 

 and where shade was the natural condition brown paper was rolled round the 

 outside of the jar and secured by a rubber band. These precautions were 

 sufficient to ensure the rearing of most larvae ; but in the case of eggs or of 

 very young larvae, they sometimes failed. Such failure is not to be wondered 

 at when it is recognised that mosquito larvae require a constant supply of 

 special food, consisting usually of living fresh-water algae, some species of 

 which are very sensitive to changes in the density and chemical constituents 

 of the water, or to the amount, and probably wave-length, of the light reaching 

 them. The larvae of Pyretoplwrus costalis, for example, are found breeding 

 in water rendered partially opaque by suspended matter and containing 

 motile algae. The suspended matter is not removed by the centrifuge, 

 but can be precipitated by an addition of 3 per cent, of common salt. On 



