106 



were yet alive, but no adults had issued. I added 10 cc from the stock 

 and in a few minutes all the pupae were dead. 



In other words, a mixture of 1 to 10,000 will kill larva?, but it 

 requires one 5 times as strong to kill pupae. 



" CRETOL, HASSLIGER NO. 1." 



This is one of the preparations sent me by Mr. F. B. Kilmer, presi 

 dent of the New Brunswick board of health, and it was tested on the 

 larvae and pupae of Culex pungens only. 



At a dilution of 1 to 8,000 it killed all the larvae in a few minutes 

 and all the pupae in an hour. 



" CRETOL, HASSLIGER NO. 2." 



This material is not so readily soluble as the No. 1 and forms an oily 

 or tarry surface film. I made the usual stock of 1 to 100 and tried it 

 on Culex pungens only. I added 5 cc of the stock to 500 cc of water 

 containing larvae and pupae, and in a few minutes all larvae were dead; 

 in half an hour the pupae also had succumbed. 



Both of these preparations are very fatal to pupae compared with 

 some of the others previously reported. 



SOLUBLE CREOSOTE. 



This also was sent me by Mr. Kilmer. It mixed readily with water, 

 forming the usual milky emulsion, and was reduced to the usual 

 stock, 1 to 100. It was used on Culex pungens only in jars containing 

 500 cc of water. 



To jar No. 1 1 added 5 cc of stock at 10.30 a. m. At 2.45 p. m. 

 many larvae were yet alive, all pupae were active, and many adults 

 had issued. It was only upon young larvae that this mixture had any 

 ill effects. 



To jar No. 2 I added 10 cc of stock at 10.30 a. m. At 2.45 p. m. 

 all larvae and some pupae were dead, while one adult had emerged. 

 No more adults emerged later, and all pupae were dead next morning. 

 At 1 to 5,000, therefore, soluble creosote is a good larvicide. 



"CRESOL, 100 PER CENT." 



This is one of the materials referred to as coming from the stock of 

 Johnson & Johnson, but is not a product of their manufacture. All 

 their samples mixed readily with water, and were purer grade mate- 

 rials than any of the preceding. 



I reduced the cresol to 1 to 100 and added 5 cc to 500 cc of water 

 containing larvae and pupae of Culex pungens. Eighteen hours later 

 only the small larvae were affected; some of the mature larvae had 



