482 



JOURNAL OF ECONOMIC ENTOMOLOGY 



\Vo\. 8 



The Expeeimexts 



An effort was made to use a certain set number of larvae for each ex- 

 periment but this was found to be unsatisfactory as the individuals 

 clung to the nests and were frequently injured in handling. The next 

 best method was to remove all the foliage from one or more tents and 

 then to fasten the tents to the twdgs. In a short time the caterpillars 

 migrated to the leaves and began feeding. 



Two sets of experiments were carried on to secure an even coating 

 of the poison on the leaves. In the first set the poison was weighed 

 out and placed in an aquarium jar with the water. This mixture was 

 thoroughly agitated and two small apple twigs were then immersed 

 in the suspension and placed in bottles of water to prevent wilting. 

 In the second set the poison was applied as a spray by means of an 

 ordinar}^ glass hand-sprayer. Xo difference could be noted in the 

 apparent amount of poison present on the leaves b}^ either of these 

 means of application. As soon as the foliage became dry the cater- 

 pillars were placed on the twigs. 



Each morning following, the dead larvae, measuring near an inch 

 in length, were gathered, counted, and placed in glass bottles. At the 

 conclusion of the experiments these samples were analyzed for arsenic 

 content . 



The following strengths were used: 



Series I 



2 to 50 gallons of water (L.H.A. and B.L.A.i) 10.3 grams to 2000 cc. H2O 

 2 to 100 gallons of water (L.H.A. and B.L.A.) 5.18 grams to 2000 cc. H2O 

 2 to 200 gallons of water (L.H.A. and B.L.A.) 2.59 grams to 2000 cc. H2O 

 2 to 400 gallons of water (L.H.A. and B.L.A.) 1.295 grams to 2000 cc. H2O 

 2 to 800 gallons of water (L.H.A. and B.L.A.) .6475 gi'ams to 2000 cc. H2O 



The first three sets were apphed April 22, the other two April 23, 1915. 



Series II 



2 to 50 gallons of water (L.H.A. and B.L.A.) 2.59 grams to 50 cc. H2O 

 2to 100 gallons of water (L.H.A. and B.L.A.) 1.281 gi'ams to 50 cc. HjO 

 2 to 200gaUonsof water (L.H.A. and B.L.A.) .647 gi'ams to 50 cc. H.O 

 2 to 400 gallons of water (L.H.A. and B.L.A.) .3237 grams to 50 cc. H2O 

 2 to SOOgallonsof water (L.H.A. and B.L.A.) .1618 grams to 50 cc. H2O 

 2 to 1200 gallons of water (L.H.A. and B.L.A.) .1067 gi^ams to 50 cc. HgO 



The first series was applied ^lay 5; the other five ^lay 4. 



The larvae were gathered each day from paper placed under the 

 vessels containing the twig. The data obtained are tabulated as 

 follows : 



1 L.H.A. =Lead H3-drogen Arsenate; B.L.A. =Basic Lead Arsenate. The former 

 contains approximately 33 per cent arsenic oxide, the latter 25 per cent. 



