ENTOMOLOGICAL SOCTETY OF ONTARIO. 59 



as to the importance and possible practicability of his scheme, Dr. Laraborn at once placed 

 $200 in the hands of M. K. Jesup, president of the American Museum of Natural His 

 tory, New York, to be paid by him in three prizes of $1.50, $30 and $20 for the three best 

 essays based on original observations and experiments on the destruction of mosquitoes 

 and flies bt/ other insects ; the prizes to be awarded by Dr. H. C. McCook, Vice-President 

 of the Academy of Natural Science, Philadelphia, and Dr. J. S. Newberry, President of 

 the New York Academy of Science. A circular was accordingly prepared in July, 1889, 

 and sent to the working entomologists of the country, embodying the conditions and the 

 object of the contest. The time given to respond was five months. It is not stated how 

 many took part in the contest, but at the end of the time given, awards were made as 

 follows : first prize to a lady, Mrs. C. B. Aaron, of Philadelphia, and the second and third 

 equally divided between Mr. A. C. Weeks and Mr. Wm. Beuteamiiller, both of New 

 York City. 



These three essays, with nine plates showing several species of dragon-flies, house- 

 flies and mosquitoes in the various stages of development and the different devices sug- 

 gested for the extermination of the mosquito, along with bibliographical lists of the 

 authors quoted and literature on the subject, an article by Dr. H 0. McGook, and a 

 letter from Capt. Macaulay, were published by D. Appleton tt Company, New York, 

 under the title of " Dragon-Hies vs. Mosquitoes," in a handsomely bound octavo vol. of 

 200 pages. 



Mrs. Aaron's experiment with petroleum is so interesting and valuable that we feel 

 constrained to make the following quotation. On page 63 she says : "The United States 

 Department of Entomology and the various State reports, as well as nurrerous entomo- 

 logists abroad have long recommended the use of petroleum in some form for the extermina- 

 tion of plant lice and many other noxious insects. Petroleum emulsion, sprayed pet- 

 roleum, the naphtha compounds and others froai the same source, are prompt and deadly 

 insecticides. With this ia mind, we early began a series of tests with common illuminat- 

 ing oil on culicid lariy under all circumstances. The narration of oae series of experi- 

 ments, typical of all, will illustrate the efficacy of this treatment. In a shallow pool of 

 water with an area of ten square inclies, five pup?e, two grown larv;e and aboat six others 

 in various stages of development, were put, with them, also two immature Odonata, and 

 a number of Cyclops and Cypris. On the surface ten drops of oil were placed and were 

 observed to cover the whole area in ten minutes. At once great uneasiness was mani- 

 fested by the larger larvpe. Then they all began cleaning off the breathing tuba with 

 their jaws, with apparent disco ufort. The evid^ut effect of the oil w<is to coalesce the 

 cilia at the tip of the tube, thus miking respiration diffijult or impossible The aauoy- 

 ance, fear, agony and finally desperate frenzy, were clearly depicted by their actions. The 

 two grown larvae were dead in eight minutes ; severil of the half-growa diei in ten 

 minutes ; at the end of twelve minutes most of the remainder, save the very soaallest had 

 succumbed. The pupte had both expired in fifteen minutes. In an hour and a half every- 

 thing was dead except the Odonata and minute crustaceans; the former seemed to be in 

 in perfect condition owing to their multitudinous breathing appliances. After the oil 

 had "been put on the above area, it was at once seen thit the proportion was too great. 

 A second pool of the same dimen.sions was tried with one drop of oil which "was quite 

 enough to have the same deadly effect, though the results were not so rapidly attained. 

 The all-parvading nature of the oil was shown by the fact that on? of the larvre removed 

 to a pool of eight square inches of surface took enough oil with it to cause almost intense 

 uneasiness to the inhabitants of the otherwise fresh water. 



These experiments were tried time after time, always with the same result, and show 

 conclusively to us that oil is the great hope of nearly every mosqui'.o infested district, for 

 the following reasons : (I) Its cheapness ; (2) its deadly nature when applied to the 

 culicidfe ; (3) its comparatively harmless nature a? applied to other form? of aquatic life; 

 and (4) the ease with which it can be applied. 



It is obvious that the time allotted was far too short to admit of much original 

 observation or experiments along the lines of the scheme which brought forth the call for 

 the contest. Had the time been two years instead of five months and the prize corres- 

 pondingly great, the results would hive been much more important and the conclusions 



