THE MEDITERRANEAN FRUIT FLY. 11 



At this season by far the larger number pass through these stages 

 in 18 to 20 days. At an average mean temperature of 68° F., which 

 is about the coolest temperature in Hawaii where fruits are gener- 

 ally grown, the immature stages require 40 to 69 days. 



Just what the length of the immature stages may be in cooler 

 regions can not be definitely stated, but experiments indicate that it 

 may be considerably increased. The egg stage has been increased 

 from a normal of 2 days at Honolulu in summer to 25 days by the 

 application for 22 days of a temperature of 48° to 53° F. A well- 

 grown larva survived a temperature of 48° to 54° F. for 79 days. 

 A newly-hatched larva remained practically dormant for 57 days at 

 an out-of-door temperature ranging from 27° to 73° F. (mean 48° 

 F.), whereas in Honolulu during summer it would have remained in 

 this stage only 2 days. The fruit fly has been held in the pupa 

 stage for about two months at an out-of-door temperature ranging 

 between 38° and 72° F. (mean, about 54° F.). Had the mean been 

 about 79° F., it would have remained in the pupa stage only 9 to 11 

 days. Three larvae in very firm apples required 28, 58, and 74 days 

 to become full grown and leave the fruit to pupate at Kealakekua, 

 where the temperature ranged between 58° and 80° F. (mean, about 

 68° F.). Add to the 74 days required for larval maturity 4 days 

 for the egg stage and 20 days for the pupa stage, and one has 98 

 days, or over three months, as the time required for the fly to pass 

 through the immature stages under certain host conditions at a 

 mean of 68° F. Thus while these stages may be completed in as 

 few as 17 days, three to four months is a very conservative estimate 

 for possible length under less favorable climatic conditions, or a 

 period sufficiently long to outlast the coolest seasons of the 

 semitropios. 



FRUITS, NUTS, AND VEGETABLES ATTACKED. 



The Mediterranean fruit fly is particularly injurious because it 

 attacks so many more different kinds of fruits of value to man than 

 does any other known fruit fly. In the Hawaiian Islands 72 kinds 

 of fruits have been found infested. Fortunately, the pineapple is 

 not infested, and the banana is free from attack when shipped under 

 commercial conditions. The fruit fly has been reared from the 

 following fruits: Fruits that are heavily or generally infested are 

 marked (1), those that serve quite often as hosts or of which many 

 escape infestation are marked (2), and those rarely infested are 

 marked (3). 



