Remedial Measures and Insecticides. xxvii 



examination showed that upon one cutting, out of 183 scales, but 

 four were living ; on a second cutting, out of 723, but two were 

 living ; on a third cutting, out of 579, but twenty-eight were living, 

 giving thirty-four living scales out of 1485 — a mortality rate 

 of 977.' 



I have, myself, repeatedly succeeded in disseminating the 

 disease affecting Lecaiiium viride by tying branches with diseased 

 insects on to trees on which the bug had hitherto remained quite 

 healthy. 



There are several methods by which spores of these parasitic 

 fungi may be disseminated. As in the last-mentioned experiment, 

 they may sometimes be communicated by merely transferring 

 affected branches to the neighbourhood of the healthy insects. In 

 such cases the spores are carried by the wind to their destination. 

 But in some of these fungi the spores are gelatinous and agglu- 

 tinated, in which case the wind would fail to disperse them. 

 Fungi of this kind may be crushed up in water and used as a 

 spray ; or artificial cultures may be made and mixed with water, 

 to be used in the same way. In the ordinary course of nature 

 these gelatinous spores are probably carried from tree to tree on 

 the feet of birds. 



General List of Substances and Processes Employed in 

 THE Treatment of Scale Insects. 



The Gas Treatment. 



Hydrocyanic acid gas is the material employed in this process 

 It is generated by the admixture of cyanide of potassium, sulphuric 

 acid and water. For the details of treatment I cannot do better 

 than quote in extenso from the admirable paper on ' Gas Treatment 

 for Scale Insects,' compiled by Mr. C. P. Lounsbury from his 

 personal experience as Government Entomologist at the Cape of 

 Good Hope. The process described was principally employed 

 against Aspidiotiis aiirantii — an insect that appears to be dis- 

 tinctly on the increase in Ceylon. I may add that I have followed 

 Mr. Lounsbury's directions in my own experiments with most 

 satisfactory results. 



' Generation of the Gas. — Hydrocyanic acid gas is generated by 



