380 MOSQUITOES OF NORTH AMERICA 
the best of the larvicides, namely, the petroleum products, was discredited by 
the authors in question. 
PERMANGANATE OF POTASH. 
In the last few years many substances have been experimented with, both in 
the United States and in other parts of the world, and there has been from time 
to time a newspaper notice, or a series of newspaper notices, of some new sub- 
stance which careful experimentation has shown to be of little or no service. 
In this way the use of permanganate of potash received much advertising in 1900, 
but, as one of the writers has elsewhere pointed out, as a result of careful ex- 
perimentation it was found that small amounts of the chemical have no effect 
whatever upon mosquito larve. They were, however, killed by using amounts so 
large that, instead of using a handful to a 10-acre swamp, as had been stated in 
the newspapers, at least a wagon load would have to be used to accomplish any 
result. Moreover, after the use of this large amount and after the larve were 
killed, the same water 24 hours later sustained freshly hatched mosquito larvee 
perfectly, so that even were a person to go to the prohibitive expense of killing 
mosquito larve in the swamp with permanganate of potash, the same task would 
have to be done over again a few days later. 
SULPHATE OF COPPER. 
In 1904 a publication by the Bureau of Plant Industry of the U. S. Depart- 
ment of Agriculture, on the use of sulphate of copper against alge and other 
microscopic plant life, put certain newspaper men on the wrong track and a 
number of articles were published making the erroneous statement that the De- 
partment of Agriculture recommended sulphate of copper as a perfect remedy 
against mosquito larve. So widely was this alleged discovery heralded that 
careful experiments were at once made by the Bureau of Entomology, by Doctor 
Smith, of New Jersey, by Doctor Britton, of Connecticut, and by other ento- 
mologists, with the result that the substance was found to be of very slight 
value as a larvicide, and of really no practical value whatever. 
CERTAIN PROPRIETARY COMPOUNDS. 
Several proprietary mixtures or mosquito compounds have been prepared and 
placed on sale for the purpose of destroying mosquito larve. A number of these 
have been brought or sent to one of the writers for experimentation but, consider- 
ing the cost, none of them has been of as great practical value as petroleum. 
In his report on the mosquitoes occurring in the State of New Jersey, 1904, 
Doctor John B. Smith describes a number of experiments with substances of 
this kind, notably with certain soluble carbolic acid and cresol preparations, 
with chloro-naphthaleum, and with phinotas oil, and in his report for 1907 he 
gives the results of certain experiments with a substance known as “ killarve.” 
It is not necessary, however, to consider any of these substances in this con- 
nection except to state that phinotas oil has met with considerable use, since it 
forms a milky compound with water which settles through a poo] and destroys 
