ORDER DIPTERA: THE NEMATOCERA, ETC. 55 



due to the agency of mosquitoes, would be out of place here, 

 where we are concerned only with the insects themselves 

 and with the means that are to be adopted to keep them 

 in check. 



The mosquito, like many other animals that breed in 

 a defined environment is most vulnerable in its larval stages. 

 To attack the larva is universally admitted to be the first 

 object of the sanitarian. 



There may be circumstances in which it is impossible to 

 proceed against the larvae, as in a country of illimitable 

 swamp. In such a case man must defend himself against 

 the attacks of the adult mosquitoes, and must drug himself 

 against the parasites that they harbour. 



(a) Warfare against Mosquito-larvae. 



Every medical officer should make a point of identifying, both in 

 their adult and larval stages, all the common mosquitoes of his district. 

 The most methodical procedure is to collect and rear the larvae. Rear- 

 ing can be done in wide-mouthed bottles capped with gauze. A separate 

 bottle should be used for each kind of larva, and each bottle should 

 be numbered. A piece of clean waterweed should be kept immersed in 

 each bottle to keep the water sweet, and the daily loss by evaporation 

 must be made good. In stocking the bottles, and always in adding 

 water, particular care must be taken that no (possibly predaceous) aquatic 

 animals of other kinds get in. Samples of full-grown larvs of each 

 kind must be preserved in spirit, and labelled to correspond with the 

 bottles from which they are taken. When the adults hatch out from 

 their pupal skins they should not be killed at once, lest they shrivel, 

 but they should be given a chance of feeding on a piece of fruit. 



Some mosquitoes, such as Stegomyia fasciata and Culex 

 fatigans, will lay their eggs in anything that is meant to 

 hold, or is not meant to hold, water, from the harmless 

 necessary water-butt to the dregs of an ill-kept drain, or 

 the few drops of rain that collect in an old tin or a broken 

 bottle. Even some of the malaria-carriers will breed in 

 casual pools of rain - water, and in the water - courses 

 used in irrigating gardens. Other malaria-carriers breed in 

 ponds, tanks, marshes, and the sedgy reaches of sluggish 

 rivers and backwaters. Many larvse can live quite happily 

 in brackish and salt water; even the common Culex pipiens- 

 larva has been taken in pools to which the sea has access. 



