December, '21] moznette: avocado insects 465 



sodium hydroxid, the writers' conclude that the sodium ion is not a 

 repellent to house-fly oviposition and its presence in some salt combi- 

 nations may be moderately attractive. 



Of the remaining substances-'in the list receiving more than GO percent 

 of eggs, all are fatty acids and therefore chemically kin to carbonic acid. 

 Of these acetic acid leads by a wide margin and it is worthy of note 

 that this is the acid most likely to occur in the ordinary decomposition 

 processes of vegetable matter where carbon dioxid is also liberated. 



Gravid house flies appear to be indifferent to the presence of the organic 

 bases, grain alcohol and glycerin, as might also be stated of the mixed 

 compound lactic acid. The mineral acids, hydrochloric and sulphuric, 

 appear to be moderate repellents. 



In the light of present results the writers' suggest that the female 

 house fly is attracted for egg laying by decaying organic matter in pro- 

 portion to the amount of carbonic and acetic acids liberated in the 

 fermentation processes, and that the preference for decaying vegetable 

 rather than animal matter may have its explanation in this fact. Also 

 it is possible that its predisposition for these two acids may explain the 

 fondness of the house fly for human environments generally, particularly 

 dwelling houses and livery stables. 



DUSTING VS. SPRAYING FOR THE CONTROL OF INSECT PESTS 



ON THE AVOCADO' 



By G. F. Moznette, Bureau of Entomology, U. S. Departmejit 0} Agriculture, 



Miami, Florida. 



The Avocado which is now being propagated quite extensively on 

 a com.mercial scale in Florida has like all other fruits a number of in- 

 jurious insect enemies. It is during the dry winter m.onths particularly, 

 while the trees are dormant that the grower of this fruit often experiences 

 serious trouble with a num.ber of enemies which attack his trees. Among 

 these enemies may be mentioned the Avocado Red vSpider, Tetranychus 

 yothersi McGregor; the leaf thrips commonly called in the North the 

 greenhouse thrips, Heliothrips hemorrhoidalis Bouche' and the leaf 

 hopper, Empoasca minuenda Ball. The red spider and the leaf thrips 

 confine their attacks to the upper surface of the foliage, while the leaf 

 hopper does its work on the lower surface. 



During the seasons 1918 and 1919 a number of tests were made with a 

 view to ascertaining the relative merits of several contact insecticides in 

 the dust or powdered form alone and in combination, with similar contact 



'Published by permission of the Secretary of Agriculture. 



