June, '15] 



SEVERIN-SE^•ERIN: KEROSENE TRAPS 



335 



flies will live in captivity" with leaves picked from trees sprayed with 

 the bait containing three ounces of poison, thirteen fruit-flies were 

 captured, some of which were actually observed feeding on the bait 

 in the field. These flies were placed in jars together with the sprayed 

 leaves suspended by threads at different heights. From time to time 

 water was sprayed on the sides of the jars. The results of the experi- 

 ment were as follows: Nine fruit-flies succumbed to the effects of the 

 poison at the end of the first day, one by the end of the second, but 

 the remaining three flies were still alive at the end of the third day. 



When the fruit-fly spray has been properly applied to the trees, 

 there is no conspicuous show of the bait from a distance, but a closer 

 examination of the treated trees shows thousands and thousands of 

 droplets of the spray adhering to the leaves and branches. These 

 droplets, even after the water has evaporated, will liot show the white 

 traces of lead arsenate to the naked eye. If the solution has not been 

 kept thoroughly agitated, the lead arsenate will sink to the bottom of 

 the receptacle containing the mixture and the last few pump-fulls of 

 the spray ^dll contain an excess of lead arsenate. When this material 

 is applied to the foliage, the lead arsenate in each droplet will settle as 

 a white deposit, but this will be covered by a glossy layer of sugar after 

 the water has evaporated (PI. 14, fig. 2.) A rain may now wash off 

 the sugar layer from the lead arsenate deposit and then, of course, 

 the white specks become more conspicuous. These may adhere to the 

 leaves for several weeks. In order to keep the finely divided particles 

 of lead arsenate in suspension in the solution, every second pump-full 

 of the spray was forcibly emptied against the bottom of the container. 



After the trees in the orchard had been sprayed for the fifth time 

 our attention was called to the fact that the leaves of the grapefruit 

 and peach had been injured by the spray. The leaves showed evidence 

 of brown areas as if they had been burned; later the leaves began to 

 fall from the trees and in the case of the peach almost entire defoliation 

 occurred. In the first two spraj^s, lead arsenate in paste form was used, 

 but with the last three sprays the powdered lead arsenate was used. 

 No attempt was made to determine the cause of the scorching of the 

 leaves under Hawaiian conditions. 



Shortly after the trees had been sprayed, a loud buzzing became 

 audible as one walked through the orchard. Hundreds of insects, 

 including house flies, bluebottle flies, syrphids, flesh flies, tachinids, 

 mud daubers and paper wasps, hymenopterous parasites, long-horned 

 grasshoppers, moths, an occasional butterfly, etc., were flying about 

 sucking up the poisoned bait. 



In several bulletins ^ Mally claims that in South Africa ''honey 

 bees have paid no attention to the thin film of sweets on the leaves of 



