33 



Arsenical*. — 1 pound io 100 gallons of irahr, with and without lime. 



3 



<B 



o 

 6 

 y A 



Poison. 



N urn her of larva' 

 placed on poisoned 

 food. 



8 



| 



u -x 



- s 



y 



Number of additional 

 dead larva 1 alter 6 

 days. 



Number of additional 



dead larva' after 9 

 days. 



c 

 Eh 



v- 

 O £ 



i ■- 



y 



i 



43 

 55 



Paris green, ordinary, with lime 



do '. 



Total 



20 

 44 



10 

 9 



10 

 35 





20 

 44 



100 



LOO 





64 



19 



45 





64 







100 





Paris green, ordinary, without lime. . 

 do 



Total 



Paris green, pulverized, with lime 



do 



Total 





44 



19 



44 



12 



7 

 42 



"2 



19 



44 





100 



56 





100 



45 



63 



18~ 



60 



12 



7 



49 



2 



63 



"T8~ 

 60 





100 

 100 



57 



40 20 





100 





78 



19 



55 



47 31 





78 







100 





Paris green, pulverized, without lime. 

 do 



Total 



Arsenite of copper, with lime 



do 



Total 



Arsenite of copper, without lime 



do 



Total 





46 



58 



i:, " — 

 26 29 





19 



100 



100 





74 



41 



33 





74 



100 



41 

 53 



19 

 40 



14 



12 



5 



28 





19 



40 



'"."'.'.'. 



LOO 



100 





59 



26 



33 





59 





100. 



42 

 54 



20 

 45 



18 

 32 



2 

 13 





20 

 45 





100 



100 





65 



50 



15 





65 







100 





London purple, with lime 





39 



51 



17 



50 



67 



7 



10 

 29 



5 

 13 



15 



49 



2 



1 



88 

 98 





Total 







7 



7 



39 



18 



64 



3 



96 



40 



16 



48 



IT 



21 



1 



19 



16 

 47 



"i 



1 



100 



52 



;-- do 



Total 



Arsenite of lead, without lime 



do 



Total 



98 





64 



20 

 19 



ii 



32 



20 



63 



96 



24 

 26 







4 



20 

 5 



""io" 



20 



19 



^:^_ 



100 

 100 





39 



4 



25 



10 



39 



100 



Much of the variation in the length of time necessary to effect the 

 death of larvae is explained by the condition of the larvae. If they are 

 just molting or about to molt, a day or two will be lost, and it may 

 happen that when they are put on poisoned food, not relishing it. they 

 refuse to eat before molting, so that two or three days may intervene 

 before they feed at all heartily on the poisoned food. In the case of 

 these experiments it was very evident that the larvae detected almost 

 immediately the fact of the unnatural condition of the foliage, refusing 

 to eat or eating very scantily, whereas larvae placed at the same time 

 on unpoisoned food fed with great freedom and greediness. These 

 results explain the apparently slow action of poisons on larvae which 

 every experimenter has witnessed. It simply means that the larva' 

 dislike the poisoned leaves and refuse to feed until forced to by extreme 

 5850 — No. 0' -') * 



