NICOTINE SULPHATE AS AN OVICIDE AND LAEVICIDE. 7 



100 per cent, hatched. As in experiment No. 1, many of the newly- 

 hatched larvae entered the apples and started their development 

 therein. 



EFFECTS OF NICOTINE SULPHATE ON NEWLY HATCHED LARV.« OF THE CODLING 

 MOTH IN THE LABORATORY. 



From the preceding results it is evident that nicotine sulphate is 

 not an efficient ovicide against the codling moth ; and since the eggs 

 probably hatched after the cessation of an injurious exhalation from 

 the sprayed glass plate and leaves, the newly hatched larvae perhaps 

 died of starvation, rather than from the spraying. To test the effects 

 of the exhalation from leaves sprayed one or more days previously 

 upon the newly hatched larvae, the following experiments were 

 performed : 



At 11.30 a. m. a pear-tree leaf was dipped into a solution of 

 nicotine sulphate 1 : 400, and another one into a solution 1 : 800. At 

 1.30 p. m., when the leaves were dry, 15 newly hatched codling-moth 

 larvae were placed upon each leaf. At 4.30 p. m. 13 larvae were dead 

 on the first leaf, but only 6 dead on the second leaf. The leaves still 

 emitted a nicotine-like odor. The following morning all the larvae 

 were dead and the leaves were wilted. At no time did any of them 

 try to burrow into the leaves as do larvae on leaves not treated with 

 these solutions, and they crawled away from these leaves more than 

 do larvae on untreated leaves. 



On May 4 a twig bearing foliage on an apple tree was dipped into 

 a solution of nicotine sulphate 1 : 400, and another twig into a solu- 

 tion of 1: 800. On May 14 a leaf was removed from each twig and 

 then 28 newly hatched codling-moth larvae were placed upon each 

 leaf between two watch glasses. During the first day the larvae 

 burrowed considerably in the leaves and apparently were not affected. 

 During the second day three of them died, but the leaves began to 

 wilt. During the third day all of them died, and by this time the 

 leaves had become dry. Between May 4 and 14 there had been much 

 rain and on the latter date the leaves did not emit a nicotine-like 

 odor. This experiment shows that the exhalation from the treated 

 leaves did not affect the larvae and that in all probability all of them 

 finally died of starvation. 



On May 18 the two twigs mentioned in the foregoing paragraph 

 were again dipped into solutions of the same strengths, but this time 

 soap was added at the rate of 2 pounds per 100 gallons of water. 

 On May 19 six newly hatched larvae were placed on each of two 

 detached leaves as usual. The leaves still emitted a faint odor 

 resembling that from the solutions. No larvae died that day and 

 only 4 of the 12 were found dead the following day. The leaves were 

 slightly eaten. 



