8 



BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE. 



On May 20, at 1 p. m., or the second day after the leaves had been 

 treated, 13 codling-moth larvae were placed on each of two detached 

 leaves; at 3 o'clock 6 silkworms (2 days old) were also placed on 

 each leaf; at 4.30 o'clock 10 of the 12 silkworms were dead, but not 

 one of the codling-moth larvae had succumbed. The following morn- 

 ing all of the silkworms were dead, but only 12 of the 26 codling- 

 moth larvae had succumbed. The leaves were slightly eaten. 



On the third day after the leaves had been treated the preceding ex- 

 periments were repeated. On this date only a few of the silkworms 

 and none of the codling-moth larvae died. The following morning 

 all of the silkworms were dead, but the codling-moth larvae did not 

 die till later, when the leaves began to dry. 



On the tenth day after the leaves had been treated the codling- 

 moth larvae tested apparently were not affected. 



On various dates many small pears (22 mm. in diameter) with the 

 calyx cups yet open were picked and then sprayed with solutions of 

 nicotine sulphate. Some of these solutions contained soap in the 

 proportion of 2 pounds to 100 gallons of water. The stem of each 

 pear used was inserted into a small bottle containing water. From 

 one to seven days after the pears had been sprayed six active codling- 

 moth larvae were removed from the oviposition jars and then placed 

 on each pear ; unsprayed pears were used as controls. 



A glance at Table II shows that about 75 per cent of the larvae 

 tested were killed when placed upon pears which had been sprayed 

 one or two days previously. It is also seen that the mortality de- 

 creases to about 25 per cent on the sixth and seventh days. 



Table II. — Effects on newly hatched codling-moth larvae when placed upon 

 small pears previously sprayed with solutions of nicotine sulphate in labora- 

 tory. 



Number 



of days 



after 



Solution 1:400 



Solution 1:800. 



Solution 

 l:400+soap. 



Solution 

 l:800+soap. 



Control. 



spraying 

 pears 

 when 

 larvae 

 were 

 tested. 



Num- 

 ber of 

 larvae 

 tested. 



Larvae 



found 



dead on 



pears. 



Num- 

 ber of 

 larvae 

 tested. 



Larvae 



found 



dead on 



pears. 



Num- 

 ber of 

 larvae 

 tested. 



Larvae 



found 



dead on 



pears. 



Num- 

 ber of 

 larvae 

 tested. 



Larvae 



found 



dead on 



pears. 



Num- 

 ber of 

 larvae 

 tested. 



Larvae 



found 



dead on 



pears. 



1 



18 

 18 



Per cent. 

 72.2 



77.7 



18 

 18 



Per cent. 



77.7 

 72.2 





Per cent. 





Per cent. 



IS 

 6 



Per cent. 

 0.0 



2 



18 

 6 

 6 

 6 



61.1 

 100.0 

 50.0 

 33.3 



12 

 6 

 6 



25.0 

 66.6 

 33.3 



16.6 



3 





4 



6 

 6 

 12 

 6 



50.0 

 83.3 

 25.0 

 33.3 



6 

 6 

 6 

 



50. 

 66.6 

 33.3 

 33.3 









6 



16.6 



6 









7 









1 













1 





EFFECTS OF NICOTINE SULPHATE ON EGGS OF TWO OTHER INSECTS. 



Experiments similar to those performed on the eggs of silkworm 

 moths and codling moths were also conducted upon the eggs of 



