64 DRAGON FLIES VS. MOSQUITOES. 



stages of development M-ere put. With tlieni were also 

 two immature Odonats and a number of Cyclops and 

 Cypris. On the surface ten drops of oil were placed, and 

 were observed to cover the entire area in ten minutes. 

 At once great uneasiness was manifested by the larger 

 larvse. Then they all began cleaning off the breathing 

 tube with their jaws, with apparent discomfort. 



The very evident effect of the oil was to coalesce the cilia 

 at the tip of the tube, thus making respiration difficult or 

 impossible. The annoyance, fear, agony, and, finally, des- 

 perate frenzy were clearly depicted by their actions. The 

 two grown larvse were dead in eight minutes ; several of 

 the half grown died in ten minutes ; at the end of twelve 

 minutes most of the remainder, save the very smallest, 

 had succumbed. The pupee had both expired in fifteen 

 minutes. In an hour and a half everything was dead 

 except the Odonata and minute Crustaceans ; the former 

 seemed to be in perfect condition, owing to their multitu- 

 dinous breathing appliances. After the oil had been put 

 on the above area, it was at once seen that the propor- 

 tion 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, thouo-h the results 

 were not so rapidly attained. The all pervading nature of 

 the oil was shown I)y the fact that one of the larvse re- 

 moved to a pool of eight square inches of surface took 

 enough oil with it to cause almost instant 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 mosquito infested dis- 

 trict, for the following reasons : (1) Its cheapness ; (2) 



