112 BULLETIN 536, U. S. DEPARTMENT OF AGRICULTURE. 



males. Of 2,639 adults, representing four lots examined by the 

 writers, only eight were females. Only 36 of 10,239 adults captured 

 by Severin were females. Many thousands of adults captured in 

 kerosene oil in connection with the present investigations have 

 demonstrated the worthlessness of kerosene as a factor in reducing 

 the infestation of fruit. 



While the use of kerosene to trap the adults of the Mediterranean 

 fruit fly is of no value in checking the ravages of this. pest, the writers 

 have made use of the number of males captured in traps to arrive 

 at conclusions regarding the relative abundance of adults in any 

 given area. The use of the kerosene trap for this purpose when sup- 

 plemented by other observations has a value, provided conclusions 

 are not attempted from too small a number of catches. The writers 

 have data on file covering the number of flies caught in 292 traps for 

 16 consecutive months. As a rule traps hung in dense foliage of any 

 sort captured more flies, while traps hung on porches and set upon 

 stumps or in other exposed situations from 30 to 80 feet away from 

 f oliage captured only an occasional male. It would seem that in 

 countries where host trees and shrubs are less abundant than in 

 Hawaii the number of flies caught could be used as a basis for valuable 

 deductions on such subjects as seasonal abundance and migrations of 

 adults. 



Description of trap.— The trap used by the writers is a simple affair consisting of an 

 ordinary pie tin suspended by three tin strips from a tin cone through the top of which 

 extends a wire by which the entire trap may be suspended from a branch. A trap 

 can be made cheaply by any tinsmith. If properly painted, traps will last several 

 seasons. The pan may be removed as often as desired. In Honolulu the oil was 

 replenished every 2 or 3 days. In dry areas no protective covering for the pan 

 containing the oil is needed. Oil to cover the bottom of the container to a depth 

 of one-fourth of an inch is sufficient. The trap should be so long that no oil will spread 

 to the bark of the tree. 



SUBMERGENCE IN WATER. 



Submergence of host fruits as a method of control has been recom- 

 mended many times by writers and investigators of fruit flics. 

 Harris recommended weighting sacks of infested fruit and sinking 

 them at sea. Gurney found that larvae in sea water in test tubes 

 pupated at the surface against the glass and that a large percentage of 

 larvae in oranges submerged in cold water for 6, 8, 24, and 45 hours 

 survived, pupated, and matured into normally healthy adults, and 

 concluded that no casual treatment such as throwing infested fruit 

 into a stream can be considered an effective method of destroying 

 fruit-fly larvae. Severin showed that many well-grown larvae found 

 floating on the top of a barrel of water, into which infested oranges 

 had been thrown 24 hours previous, resumed activity within several 

 hours after being placed on moist filter paper, in spite of the fact 



