No. 4.] GYPSY MOTH APPENDIX. 481 



The indoor experiments were roughly checked by field tests, 

 where areas of badly infested brushland were sprayed with the 

 same proportions of arsenate of lead and glucose as in the experi- 

 ments described. In these cases the killing of the larvae was 

 apparently uniform, no difference being noted between the plot 

 where glucose was not used and those sprayed with glucose solu- 

 tions. This result has been checked by an examination of the 

 locality for egg-clusters. 



In the use of arsenate of lead, as at present prepared, we are 

 dealing with an original precipitate, matter in its finest state 

 of division. The case may be compared to that of the use of 

 Bordeaux mixture, where the sulphate of lime, noted for its 

 adherence to foliage, is a fresh precipitate. Such a flocculent 

 precipitate as arsenate of lead finds ready lodgement on the irreg- 

 ularities of the foliage, even attaching itself to the leaf -hairs, and 

 after a few hours dries down to a varnish-like film, which adheres 

 until the leaves drop. I do not recall any other insecticide that 

 would destroy leaf-eating insects fifty-two days after the time of 

 spraying. 



To summarize : from the various tests described, we are unable 

 to attribute any especial value to glucose as an ingredient of 

 spraying mixtures containing freshly prepared arsenate of lead. 

 The fact that the glucose disappears from the foliage after the 

 first shower shows that its effect, if there is any, is transitory. 

 The final determination of the matter can best be reached by the 

 extensive spraying operations of a season ; but, from the results 

 above recorded, it would seem to be more economical to abandon 

 the use of glucose. 



