100 



territans and late in the season some Anopheles punctipennis devel- 

 oped. 



In the beg-inning of the season the new pails seemed to offer no 

 attraction to the insects, while last year's pails, all blackened inside, 

 were always fully stocked from the start. 



Into one of these old pails I dropped a small quantity of slaked lime, 

 not enough to make the water milky or to cause any obvious change 

 in its appearance. Next morning I found a thin lime scum on the 

 surface, no living larvae, and two new agg boats, from which no larvae 

 ever developed. The pail was open to sun and rain, and a week later 

 the lime coating was gone and a new lot of young larvae was observed. 



The experiment was duplicated in one of the new pails, and for over 

 a month the pail had no trace of larvae. In fact, to start it at all I 

 washed it out and added a little garden soil, with a tuft of sod and a 

 little torn grass. That proved effective at once, and next morning 

 there were two or three Qgg boats on the surface. 



The use of lime may under some circumstances be very convenient 

 and effective, especially in foul pools on dumps and in cesspools. So 

 long as there is enough to form a scum no mosquito larva, Culex., or 

 Anopheles can develop. 



An incidental observation in this connection may prove of interest: 

 A little keg that had contained "Calcothion," which is a ready-made 

 ime, salt, and sulphur mixture, was left outdoors and became nearly 

 filled with rain water. After a few days this swarmed with larvae, 

 Iwhich gathered their food from the lime-coated sides of the barrel and 

 reached the pupal stage before I interfered. 



COPPERAS. 



Several experiments were made with this material, but the record 

 slips were accidentally destro3'ed. The result was not encouraging, 

 however, as very large quantities were required to destro}^ the larvae, 

 and I did not feel at all certain that the larvte were not simply starved 

 out by the destruction of their food supply. 



CRUDE PETROLEUM. 



The subject of the petroleums has already been touched upon and is 

 introduced into this series only to record a small test that was made 

 with an old oil from which the volatile parts had pretty well escaped. 

 This was dropped on the surface of a pail of water to test its spread- 

 ing power, but it remained persistently in globules and drops and for 

 over an hour did not change at all. Then I stirred up the mixture 

 thoroughly, breaking up the oil into fine globules, but yet it formed 

 no film and killed only a few larvae. After yet an hour I stirred up 

 the whole mixture once more, and finally, six hours afterwards, all 



