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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



A comparison of Tables II and III shows that the Mediterranean 

 fruit-flies had again increased in numbers during the five weeks in 

 which no spray was apphed to the fruit trees. An examination of the 

 fruit trees of this orchard after these five weeks had elapsed showed 

 that some of the fruit had again been ''stung." Trapping the pest 

 ^ith kerosene was continued in this orchard in connection with other 

 experiments, and fifteen weeks after spraying was discontinued, 642 

 fruit-flies were captured in three days in the ten traps, or an average 

 of 214 per day. 



The gradual increase in the number of JMediterranean fruit-flies in 

 this orchard after spraying was discontinued may be attributed to a 

 number of causes: (1) horticultural sanitation was not rigidh^ prac- 

 ticed and man}^ trj^petids emerged from the fallen, infested fruit; (2) 

 this orchard was not isolated but was adjacent to a very much neg- 

 lected orchard from which probably manj^ flies migrated; and (3) 

 fruit -flies breeding in the wild fruits, covering thousands and thousands 

 of acres in the mountainous districts, were probably caught up hy the 

 winds and carried into this orchard. We ^ have published the results 

 of an experiment on the flight of two thousand marked, male, Mediter- 

 ranean fruit-flies and have demonstrated that marked specimens, set 

 free from the side of a mountain at an elevation of 350 feet, were 

 carried by the prevaihng winds. Some of these marked insects were 

 captured in kerosene traps in this orchard, a mile from the point of 

 liberation. 



After taking Weinland, California's representative stationed in 

 Honolulu, into an orchard and showing him our methods of checking 

 up the effectiveness of the poisoned bait spray by means of kerosene 

 traps and the results obtained, this entomologist carried on a similar 

 experiment in a residential section of Honolulu. Weinland ^ sprayed 

 onty the low host trees, for with the apparatus at hand ''it was impos- 

 sible to spray higher than ten feet." He plotted a curve in checking 

 up the efficiency of the spray ^\dth the use of kerosene traps and WTites, 

 "From the shape of the curve, it is apparent that there is a marked 

 but temporary reduction in the number of flies caught. The lowest 

 point comes about flve days after sprajdng, after which time the spray 

 becomes ineffective and flies coming in from outside sources raise the 

 number again." 



In our work, Mally's ^ formula of the poisoned bait spray was 

 adopted but with this difference, Mally used three ounces of lead 

 arsenate and we increased the amount from three to five ounces after 

 the application of the first spray. The amount of poison was increased 

 in our work in order to kill the flies more rapidh^ by giving them a 

 greater dose of poison. To determine the length of time that fruit- 



