296 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



pound acted as a repellent to the adults, the latter preferring to ovi- 

 posit in unsprayed leaves when given a choice. Still further tests 

 this year have also shown that while oviposition will take place when 

 females are confined with plants completely covered with Bordeaux, 

 yet very few eggs are laid under such circumstances. 



Table I. — Comparison of Oviposition of E. tnali on Plants Completely Sprayed With Bor- 

 deaux Mixture and on those partly sprayed 



The above table summarizes results obtained in 22 experiments in 

 which a total of 72 fertile females were used and 371 hatchings obtained. 

 In these tests the insects were all examined under a lens to see whether 

 they were gravid or not and only the former were included in the tests. 

 The same number was placed in each cage on plants that were known 

 to be free from mali eggs from other sources. All insects were removed 

 after a ten days' period and the hatching young were counted daily. 

 Where there was a choice between sprayed and unsprayed leaves by 

 far the majority of eggs were laid in the latter, the ratio being approx- 

 imately six eggs per female for the ten day period in unsprayed leaves 

 as against one egg per female in the sprayed. Where no choice was 

 given the average was slightly higher on the sprayed leaves but here 

 there were always some eggs laid in the unfolding leaves at the tip 

 of the plant wh^ch were unavoidabty partly or entirely free from 

 the spray. 



It was then decided to test out the action of Bordeaux mixture on 

 these insects in more detail. Potato plants were sprayed thoroughly 

 with this compound. Both the 4-4-50 self-prepared formula and several 

 commercial dry Bordeaux powders that were mixed with water were 

 used. Single leaves from plants thus treated were placed in shell 

 vials with individual leafhoppers. It was soon observed that there was a 

 surprising mortality amiong the n\Tnphs and as a result more vials were 

 started, the exact instar of the nymph in each case being noted. The 

 following table is shown to illustrate one experiment out of several 

 that were conducted. In all about 100 insects were used in these 

 tests and the writers feel that the results although preliminary are 

 yet of sufficient interest to be presented here. 



