58 THE REPOET OF THE. No. 36 



undrained marsh yields an average of about .7 of a ton of coarse hay, which hardly, 

 repays the cost of cutting and marketing, while the drained marsh produces 2.6 tons 

 of a much better grade, involving an increase of about $15 an acre. It should; 

 of course, be recognized that an average of about three years is required to realize 

 the full benefit. 



Conclusions. 



Present methods of mosquito control are sufficiently effective to afford much 

 relief from the mosquito pest by freeing protected communities to a very large 

 extent from mosquito annoyance and mosquito-carried diseases. Such results can 

 be obtained only when the matter is gone about in a careful systematic manner, 

 involving a thorough study of the nature of the problem and the creation of an 

 effective organization to carry out the work. 



Mosquito control work, because of the large amount of temporary control 

 involved, must become a permanent fixture. 



With present methods of control the protected territory will at times be 

 troubled by some mosquitoes, because the enormous increase in breeding surface, 

 brought about by a prolonged rainy period, may be such as the organization cannot 

 <;ope with. 



More thorough or fundamental studies of the life economy of the economic 

 species of mosquitoes are needed in order that still more effective methods of control 

 may be found. 



Mr. Gibson : May I ask whether you have used oil to any great extent on 

 the marshy areas? 



Dr. Headleb. Oil is used extensively for temporary elimination in small 

 temporary pools, basins, in the treatment of garbage dumps, and to some extent, 

 ■although only a minor extent, on the salt marsh. It is considered a, method 

 of temporary elimination only, and its use is no more extensive than we can 

 avoid. We use a good many thousand barrels of oil in a year, because there is 

 much temporary work to be done, and I think if we take into consideration 

 existing conditions there always will be temporary work to be done. There are 

 always temporary pools under exceedingly rainy conditions, and these pools are 

 breeding grounds for the mosquitoes. We have had the question raised frequently 

 as to why we do not reduce the seed or eggs so that under these extra rainy 

 conditions they could not produce so many insects. We have not got the eggs 

 ■down far enough yet to notice much difference, although we have made a number 

 of experiments; 



Prof. Caesar: What type of oil do you use now? 



Dr. Headlee: All kinds of fuel oil. Eecently the Standard and other 

 concerns have been making us an oil up to heat strength by putting in a good 

 amount of crude kerosene. We need an oil with a large amount of spread 

 in proportion to holding power, and we are continuously trying all kinds 

 of oil, for until we test it out we do not know the character of it and 

 whether or not it will suit our purpose. The number of fuel oils is tremendous, 

 «,nd the only way we can get the kind we want is to have samples submitted 

 to us and test them for spread and for staying qualities. Some oils will stay 

 for two weeks, and others for two days, some will spread out nicely by themselves, 

 others will have to be sprayed on to make them spread at all. The whole question 

 is a difficult one, and we have tried to get satisfaction from the standpoint of 

 ■viscosity, but the oil people do not seem able to give us just what we are looking 



