MEDITERRANEAN FRUIT FLY IN HAWAII. 75 



been found most unusual. In the laboratory and out of doors adults 

 feed and oviposit at all times of the day during the warmer months. 

 Lounsbury has stated that in South Africa adults seek shelter 

 beneath dried leaves, etc., in rearing cages during the colder weather, 

 and Compere has observed adults active on orange trees in Spain 

 during the warm hours of a day following freezing night temperatures. 



LENGTH OF LIFE CYCLE. 



During the warmest Hawaiian weather, when the mean tempera- 

 tures average about 79.5° F., the egg, larva, and pupa stages may be 

 completed in as few as 13 or as many as 33 days, according to the 

 individual and its host. At this season large numbers pass through 

 the immature stages in from 18 to 20 days. As the length of the 

 adult life has been found to vary from a few days to 230 and 315 days, 

 it is evident that the life cycle may be as long as 1 1 months when the 

 fly passes its immature stages during the warmest portions of the year. 

 At an average mean temperature of about 68° F., which is the coolest 

 mean found by the writers where host fruits were readily available 

 for study, the immature stages required from 40 to 69 days. Data 

 already discussed indicate the difficulty in stating just what varia- 

 tions there may be in the length of the life cycle in still cooler climates. 

 Thus the egg stage has been increased from 2 to 24 or 25 days by the 

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

 third-stage larva survived a temperature of 48° to 54° F. for 79 days, 

 while another larva remained in the first instar 57 days at an out-of- 

 door temperature ranging from 27° to 73° F., with a mean of about 

 48° F. The fruit fly has been held in the pupa stage at an out-of-door 

 temperature ranging between 38° and 72° F., with a mean of about 

 53° to 54° F. for about 2 months. At Kealakekua, where the tem- 

 perature ranged between 58° and 80° F., with a mean of about 

 68° F., 3 larvae in very firm apples required 28, 58, and 74 days to 

 become fully mature and leave the fruit to pupate. 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 a cycle for these stages of 98 

 days, or over 3 months. A very conservative estimate for the pos- 

 sible length of the immature stages, or a period sufficiently long to 

 outlast the coldest seasons of semitropical regions, is 3 to 4 months. 



SEASONAL HISTORY. 



In littoral Hawaii there may be as many as 15 or 16 generations of 

 the Mediterranean fruit fly each year, provided one considers the 

 length of a generation as extending from the time the eggs are de- 

 posited until the female of the next generation begins to oviposit. 

 With such an understanding a generation at Honolulu may require 

 under the most favorable conditions as few as 17 days during the 

 warmest weather, or as few as 31 days during the coolest winter 



