February, '19] 



WOGLUM: LIQUID HYDROCYANIC ACID 



121 



the determination of which was undertaken entomologically by obtain- 

 ing data on scale-kill in different parts of tented trees. The results are 

 in part herewith presented: 



Table I 



Table showing the mortality of purple scale (Lepidosaphes beckii) at 

 different heights above the ground on trees fumigated with liquid 

 hydrocyanic acid. The females were largely in the egg stage and each 

 adult with its egg quota was considered a unit : 



Dosage — Appro.ximately schedule I for sodium cyanid. 



Exposure — 85 minutes. 



Temperature — 70°. 



Inspectors — R. S. Woglum, M. B. Rounds. 



The results of this experiment show that in each of the seven trees, 

 the scale-kill was more effective toward the bottom of the tree than 

 toward the top. Out of a total of 1452 insects at 1 to 2 feet for all the 

 trees, 3.4 per cent were Uving while at 8 to 11 feet, 8,85 per cent of the 

 2689 examined were alive. Thus the percentage of living insects 

 toward the top of the trees in these tests is noticeably greater than 

 towards the bottom, which would indicate that the difference in gas 

 density is proportionally pronounced. 



Table II 



Table showing the mortality of red scale {Chrysomphalus aurantii) 

 at different heights from the ground on small trees fumigated with 

 liquid hydrocyanic acid. Totals of six trees: 



