56 ENTOMOLOGY FOR MEDICAL OFFICERS 



Many species — chiefl\- jungle-mosquitoes of no account to the 

 medical officer — deposit their eggs in the water that collects 

 in holes in stumps and forks of trees, in the hollows of 

 bamboos, in the curious leaves of pitcher-plants, and sundry 

 such places ; but even Stegomyia fasciata will breed in places 

 of that kind. 



A strict enforcement of ordinary sanitary regulations 

 will do much to extinguish, in any given locality, the species 

 that depend upon house water, drains, and puddles. Wells, 

 cisterns, and water-butts must be kept covered, holes must 

 be filled in, surface drains must be kept clean, jungle must 

 be cleared away, and broken crocks and old tins and every- 

 thing of that sort must be stamped fiat and buried. Where 

 cesspools exist they must be treated with petroleum. 



Beyond the immediate precincts of the house all un- 

 necessary ponds must be filled in, and surface drainage must 

 be looked to. Village tanks that are required for use can 

 be treated at regular intervals with petroleum, a thin surface- 

 film of which is said to clog and choke the breathing-holes of 

 the larvae. 



Drinking-tanks, which would be spoilt by petroleum, 

 can be treated from time to time with sulphate of copper : 

 it has been found in several places that this salt in a solution 

 too diluted to affect the most sensitive human stomach 

 makes life difficult for mosquito-larvae by destroying the 

 minute algae that form the staple of their food. 



In brief, it is admitted by all reasonable people that the 

 chief thing is to make life impossible for mosquito - larvK 

 by clearing, draining, and levelling, by strict attention to 

 sanitary minutiae, and by instituting a domestic water- 

 supply that is independent of wells and ponds. 



As to natural enemies of mosquito-larvae: no zoologist 

 is disposed to question the established " laws " of Nature, or 

 to dispute the obvious truth that in nature mosquitoes, like 

 all other forms of life, must be kept within bounds by com- 

 petitors and foes. But the existence of civilised man is 

 a standing protest against the works of Nature, and it seems 

 doubtful whether in his operations against mosquito - larvje 

 any more than in his struggles against the many other ills 

 that flesh is heir to, the medical officer will get much comfort 



