334 Report of the Department of Entomology of the 



Results. — There was no marked difference in the speed of action 

 of the different combinations with the exception of the zinc arsenite 

 and molasses. With this preparation 60 per ct. of the beetles 

 succumbed within twenty-four hours, while with the other mixtures 

 no insects died until the second or third day. After this period 

 usually one or two of each lot would be found dead every day. A 

 moderate amount of feeding occurred during the first twenty-four 

 hours, then the beetles ceased to feed and remained inactive, as if 

 hibernating, until death ensued. 



Test No. 2, with Mamestra picta. — In this test, the purpose was 

 to determine the effects of zinc arsenite and lead arsenate alone or 

 in combination with either sugar, soap or glue. As the insects had 

 been taken on cabbage, seedlings of this plant were used as food. 

 The observations were continued for four days. 



Results. — No appreciable difference was detected in the rate of 

 action of the arsenicals on this species. It should be mentioned 

 that neither sugar, soap nor glue influenced materially the effective- 

 ness of the poisons. The toxic properties of the zinc and sugar 

 combination were shown in twenty-four hours by the death of one 

 larva, while the poisonous effects of the other mixtures were not 

 apparent until forty hours. Notwithstanding these differences at 

 the start, all the combinations were practically of equal effectiveness 

 at the expiration of four days. 



Test No. 3, with Hy-phantria cunea, was made to determine the 

 comparative values of the following combinations: lead arsenate, 

 paste, with water, soap, glucose and glue; lead arsenate, dry, with 

 water, bordeaux and lime-sulphur; and zinc arsenite with water, 

 bordeaux, lime-sulphur, soap, glucose and glue. Trees in the nursery 

 were sprayed with these mixtures and on the same day some foliage 

 of each was brought to the laboratory and fed to the caterpillars. 

 The rate of action of the different mixtures and the relative con- 

 sumption of food is indicated in Table I. 



Results. — Attention is called in this experiment to the similarity 

 in action of the poisons and the irregular amount and character of 

 feeding. However, considering both the appearance of the cater- 

 pillars at the end of the test and the number killed, there is a slight 

 difference in favor of the zinc combinations. The maximum feeding 

 occurred with zinc arsenite, zinc arsenite and glue, and lead arsenate 

 and glucose. The minimum amount of foliage was consumed where 

 mixtures of lime-sulphur or bordeaux with either poison had been 

 applied. These results indicate a greater repellent action by the 

 last-named combinations. This repellent property was apparent 

 also in the manner of feeding, for check larvae fed from the upper 

 surface, leaving the lower epidermis intact; while, as will be noted 

 in the table, the larvse in some experiments fed only from the under 

 surface or ate holes in the leaf, consuming both the upper and lower 

 epidermis. 



