aVIEDITEBRAXEAN FRUIT FLY IN HAWAII. 117 



able. One female deposited 622 eggs between June 4 and September 

 2. The long adult life, and the ability of the female to deposit eggs 

 regularly succeeding the period of from 4 to 8 days after emergence 

 which is required to oomplete sexual maturity, make it possible for 

 the annual progeny of a single pair of adults to reach enormous 

 numbers. 



Attempts at control by clean culture have been failures, owing 

 largely to insurmountable obstacles placed in the way of man by a 

 favorable climate and an unprecedented quantity of varied host 

 fruits. Many fruits and nuts subject to attack grow on huge trees 

 which blossom irregularly, and produce, in many instances, fruit 

 susceptible to attack throughout the year. There is no procedure 

 by which clean culture may be made effective under the present 

 Hawaiian cultural methods. The islands are thoroughly overrun 

 with the fruit fly, and this applies quite as much to the wild guava 

 scrub in pastures, on lava flows, and in mountain valleys and ravines, 

 as it does within the city limits. By far the larger number of host 

 trees and shrubs aie grown more for the protection they offer from the 

 semitropical smi and for their ornamental value than for their 

 inedible fruits. The destruction of host vegetation will not be 

 practicable until it can be demonstrated that a distinct advantage 

 would be gained thereby. To destroy all host trees of Honolulu at 

 the present time would be to remove a large percentage of her prized 

 vegetation without any compensating returns. 



The ideal climatic and host conditions of Hawaii have rendered 

 less effective and impracticable the usual artificial methods of con- 

 trol the value of which has been demonstrated in other countries pos- 

 sessing natural features less favorable to fruit-fly increase. At the 

 present time the only hope of relief lies in the establishment of para- 

 sites. Six parasites have been introduced during the past three 

 years and are now well established. While they have more than 

 repaid the Territory of Hawaii for the cost of their introduction by 

 bringing about an improved condition in the coffee-growing industry, 

 it is doubtful whether they will effect a sufficient decrease in the 

 proportion of infested host fruits to be considered efficient factors 

 in control. This conclusion appears inevitable in spite of the remark- 

 able success attendant on their introduction, unless a campaign is 

 inaugurated for a reapportionment of host fruits; otherwise the hordes 

 of adult flies maturing in thick-meated fruits, or in fruits protecting 

 larvae by other means from attack by parasites, will neutralize the 

 effective work of parasites attacking larvae in thin-skinned and thin- 

 pulped fruits. There is great need of an effective egg parasite that 

 will kill the fruit fly before the larva can do injury. 



From a practical or commercial standpoint the results of the inves- 

 tigations reported herewith are of value (1) in furnishing data to 



