158 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



worm (Hyphantria cunea Dru.), zebra caterpillar (Mamestra picta 

 Harris), and willow beetle {Lina scripta Fab.). This paper deals with 

 the effects of these compounds on the insects and on apple foliage. 

 The results of the feeding tests are briefly summarized as follows : 



(1) The most striking difference in the action of the poisons was 

 noted in several experiments when the caterpillars were on the tree 

 at the time of treatment or placed on the foliage while it was wet with 

 the spray. Under these conditions the zinc had double the speed, 

 as compared with the lead poison. This difference was not so notice- 

 able with larvae of the willow beetle. 



(2) In all of the other feeding tests there were no important differ- 

 ences regarding speed of action in favor of either poison. The re- 

 sults varied but the zinc combinations were slightly quicker in most 

 experiments. 



(3) Likewise there was no great difference in the sticking properties 

 of these poisons. The adhesive quality was very well shown in some 

 tests in which the sprayed foliage was subject to the action of the 

 weather for periods of 3 days, 8 days and 24 days. The conspicuous 

 result of these latter experiments is that, both when first applied and 

 when subject to weather action, zinc arsenite or arsenate of lead used 

 alone were equal in effectiveness. 



(4) All the combinations were at first more or less repellent, but when 

 exposed to the weather the poisons in question, either singly or with 

 lime-sulphur, soon lost this quality and became more attractive to the 

 caterpillars; while with combinations containing bordeaux and soap 

 there was only a slight loss in the repellent properties during the 

 experiment. With most of the combinations a reduction in efficiency 

 was coincident with the loss of the distastefulness of sprayed foliage. 



In our spraying experiments zinc arsenite did not injure apple foliage 

 when used with lime or with bordeaux mixture. There was slight 

 marginal injury in one experiment with lime-sulphur. In all of the 

 other tests where zinc was used alone or in combination with soap or 

 glucose there was more or less browning of the margins of the leaves 

 with crescentic rings about ruptured areas in the epidermis. 



President W. D. Hunter: This paper is before the Association 

 for discussion. 



A. W. Morrill: I have been especially interested in arsenite of 

 zinc during the past season in connection with the control of the 

 bean lady bug. The foliage of the bean appears to be unusually 

 susceptible to injury by arsenical insecticides. Our experiments so 

 far are not conclusive, but the brands of zinc arsenite so far tested 

 on the bean have been a little more injurious than arsenate of lead. 



