41 



On the 5th of July of the present year I noticed for the first time a few mosquitoes 

 on the porch of my cottage, in the Catskill mountains of New York. The elevation of 

 this cottage is about 2,500 feet, and mosquitoes have hitherto been rare visitors. The 

 month of June, however, was very wet, and as I had noticed several pools of surface 

 water in the immediate vicinity, the presence of these mosquitoes caused me some 

 anxiety, as I feared they would continue to breed throughout the summer and prove a 

 serious annoyance later in the season. One of the surface pools mentioned was situated 

 on my own grounds, and upon first noticing the mosquitoes I walked out to this spot. 

 It was about dusk, and about a dozen or more female mosquitoes were found buzzing 

 about the surface of the water. I immediitely sprinkled four ouaces of coal oil upon the 

 surface of the pond. 



Upon the following day I carefully measured the little pool and found that it con- 

 tained 60 square feet. From day to day until July 15th, when I returned to Washington, 

 observations were made. Severe rain-storms occurred on the 8th and lOtli of the month, 

 and after the first of these the pool lost the glassy irridescent surface effect given by the 

 almost continuous but infinitesimally thin layer of kerosene. Nevertheless the insecti- 

 cidal effect of the latter did not seem to diminish, although I could no longer perceive any 

 coal oil odor. Many dead insects were found floating upon the surface of the water the 

 next morning after the application, and these increased rapidlv up to the time of my 

 departure. The pool, which upon the evening of the 5th had been teeming with animal 

 life, contained no living insects during the following ten days. 



The actual good accomplished is shown by the following facts : All aquatic larvae, 

 including those of the mosquito, were killed. The kerosene, curiously enough, seemed 

 to exercise no deterrent effect upon the adult female mosquitoes. They still continued 

 to attempt to deposit eggs and in this attempt were destroyed. This is, in my opinion, a 

 most important point, and one which has hardly been anticipated. 



On the tenth day after the application a careful count of the dead insects floating upon 

 the surface of the water was made over a restricted portion, and from this count the 

 entire insect surface contents of the pool was estimated, with the following result : 



Entire number of dead insects floating on the surface 7,400 



Number of mosquitoes 370 



Number of Epirrita inclinata, Walker — a small Geometrid moth 148 



Number of Heterophleps friguttata, H.S. — another small Geometrid .... 42 



Number of Chrysops hilarls, O.S. — a common gad fly of the region 27 



These were the most conspicuous. The others were mainly minute NematocerouS 

 Diptera, although there were a large number of small Heterocerous Lepidoptera, a few 

 aquatic Coleoptera — the largest species being the Dytiscid Agahus gagates, Aubd — and 

 also a few specimens of Cryptocerate Heteroptera. 



It is difficult to say how certain of the non-aquatic specieSj particularly the Lepid- 

 optera and the Chrysops, happened to be caught. They may have visited the pool to 

 drink, or they may have been attracted to its shining surface. 



The observation, it seems to me, possesses interest not only as proving definitely the 

 efficacy of the remedy and as showing that adult mosquitoes are killed as well as their 

 early stages, but also as affording an indication as to the amount of kerosene which will 

 prove effective for a given surface of water, and also as aff'ording some indication of the 

 length of time for which a single application will be operative. It is true that upon 

 this last point the observations were not complete, owing to my departure after ten days, 

 but as already indicated, the influence of the kerosene outlasted all ocular or odorous 

 evidence of its presence, and there is every reason to suppose that it would have con- 

 tinued for some days longer. 



As a general thing, in larger ponds, which are of a more permanent character, the 

 presence of fish is a check upon the multiplication of the mosquito. These insects breed 

 mainly in marshy lands, where small pools, surrounded by wet soil, adjoin each other, 

 and such spots, where accessible, can be readily and economically treated with coal oil. 



