NICOTINE SULPHATE AS AN OVICIDE AND LAEVICIDE. 11 



the nervous s} r stem the more effective the poison. This fact probably 

 explains why practically all of the embryos that died succumbed 

 during the last stage of development. 



Feytaud (S) described five stages in the embryology of (Eudemis) 

 Polychrosis hotrana Schiff. and of (Phalonia) Conchylis ambiguella 

 Hbn., and he treated many eggs of these moths with various strengths 

 of pure nicotine and soap. The resulting mortality varied consider- 

 ably, but even the strongest solution (1 : 666) used did not prove effi- 

 cient. He tested the eggs in the various stages of development, but 

 in almost every case in which the embryos died they succumbed dur- 

 ing the last stage. 



Lovett (4) sprayed apple-tree foliage with solutions of nicotine 

 sulphate, and after several hours, when the leaves were perfectly dry, 

 he placed many small tent caterpillars {Malacosoma pluvialis 

 Stretch) on these leaves. He states that these caterpillars showed a 

 decided aversion for the sprayed leaves ; all of them soon became sick 

 and a large percentage of them died. On the third day after the 

 foliage had been sprayed more caterpillars were placed on the same 

 . leaves and similar results were obtained. The leaves were not eaten. 

 Lovett performed other experiments in which the caterpillars slightly 

 ate the leaves which had been sprayed several hours previously. In 

 this case the action of the nicotine was quick and decisive. These 

 results agree with those given in the preceding pages. 



Theoretically nicotine sulphate is nonvolatile, although we know 

 from experience that the commercial 40 per cent nicotine sulphate 

 (the kind used in all the preceding experiments) is more or less 

 volatile. Moore and Graham (7) state that pure nicotine sulphate is 

 nonvolatile, and demonstrated that its vapor or exhalation (if either 

 one is given off) did not kill the insects tested. They also state 

 that commercial 40 per cent nicotine sulphate contains from 1 to 2 

 per cent of free nicotine, whose vapor did kill the insects tested. 

 Moore and Graham claim that when spray solutions are prepared 

 by using commercial nicotine sulphate, hard water, and soap, the 

 nicotine sulphate is decomposed, setting free the nicotine ; the amount 

 of decomposition depends upon the amount of alkalies contained in 

 the solutions. This view easily explains the presence of a thin film 

 (already mentioned several times) left upon evaporation of the 

 spray solution, which is certainly the nonvolatile portion of the 

 nicotine sulphate contained in the solution. For some time after 

 the application of the solution the film continues to emit an odor 

 and its exhalation is more or less toxic to young larvae, showing 

 that it is not pure nicotine sulphate according to Moore and Graham. 

 Moore and Graham (7) state that 12 days after lettuce in a green- 

 house had been sprayed with a solution of commercial 40 per cent 

 nicotine sulphate, it still bore nicotine. 



