58 



insect in all its phases may be instantly killed by contact with minute quantities ot 

 permanganate of potash. It is claimed that 1 part of this substance in 1,500 of 

 solution distributed in mosquito marshes will render the development of larvae 

 impossible; that a handful of permanganate will oxidize a 10-acre swamp, kill its 

 embryo insects, and keep it free from organic matter for thirty days, at a cost of 25 

 cents; that with care a whole State may be kept free of insect pests at a small cost. 

 An efficacious method is to scatter a few crystals widely apart. A single pinch of 

 permanganate has killed all the germs in a 1,000-gallon tank. 



The item is so obviously ridiculous upon its face that it would hardly 

 seem worth while to make any attempt to refute its statements. Nev- 

 ertheless, it has been so widely read that definite experimentation 

 seems necessary to set the matter at rest. The unknown author's 

 ignorance of the life history of mosquitoes in the opening sentence 

 need not necessarily imph^ that he would not know a good remed}' if 

 he found one. Careful experiments were undertaken by the writer 

 in July, 1898, with various strengths of permanganate of potash in 

 water containing mosquito larvffi from one to six days old. It was 

 found that small amounts of the chemical had no effect whatever upon 

 the larvte, which were, however, killed by using amounts so large that, 

 instead of using a ''handful to a 10-acre swamp," 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 larvse were killed, the same 

 water twenty-four hours later, sustained freshly-hatched mosquito 

 larvse perfectly, so that even were a person to go to the prohibitive 

 expense of killing mosquito larv« in the swamp with permanganate 

 of potash, the same task would have to be done over again two days 

 later. 



The same conclusion was subsequently reached, after careful experi- 

 ment, by Dr. Lederle, of the New York health office, and by the Ital- 

 ians Celli and Casagrandi. 



Proprietary mixtures. — A number of proprietary and secret mix- 

 tures recommended for mosquito-breeding pools and which have been 

 put on the market since the wide-spread interest in the mosquito ques- 

 tion has sprung up have been tested by the writer, but none have been 

 found more satisfactory than the cheapest petroleum oil. 



Experiments of CeUland Cascujrandi. — The most extensive series of 

 experiments with culicidal mixtures which has been made was con- 

 ducted by the Italians Celli and Casagrandi, above referred to. They 

 have tabulated in the "Annali d' Igiene Sperimentale, Rome (Vol. IX, 

 Fasc. Ill, 1899, pp. 317-353), the results of experiments with man}" 

 substances. Referring to petroleum, they say that apart from the 

 question of the expense, which outside of America is worthy of note, 

 the action of petroleum in destroying mosquito larvai is not always to 

 be put in the front rank. Their conclusions are practically as follows: 



(1) Of the whole period of the cycle of development of mosquitoes the stages in 

 w'hich they are most easily destroyed are those of larvje and of the aerial mosquito, 

 and larvae are most easily killed the younger they are. 



