10 



BULLETIN- 640. U. S. DEPARTMENT OF AGRICULTURE. 



favorable to fruit-fly increase. At Honolulu the temperature rarely 

 drops as low as 58° F., and then only for a few hours during one or 



two nights in the year. 

 The daily range in 

 temperature is small, 

 averaging between 8 

 and 11 degrees, while 

 the normal monthly 

 mean temperatures 

 range between 70.9° F. 

 in the winter and 79° 

 F. in the summer. 

 Biological work has 

 shown that even the 

 lowest monthly means 

 of localities up to 1,500 

 feet elevation have lit- 

 tle effect upon the fruit 

 fly other than to retard 

 somewhat its develop- 

 ment. It is never cold 

 enough throughout the 

 coastal regions of Ha- 

 waii to render either 

 the adults or the larvse 

 inactive. There are 

 no periods of the year 

 at any Hawaiian port 

 when climatic condi- 

 tions are unfavorable 

 for fruit-fly increase. 

 A continuous temper- 

 ature of 58° to 62° F., 

 or the lowest range of 

 temperature usually 

 experienced, does not 

 increase the normal 

 mortality among the 

 larvae. 



LENGTH OF TIME REQUIRED 

 FOR DEVELOPMENT. 



During the warmest 



Fig. 10.— Three important edible fruits subject to fruit-fly attack: -rr „ • • _ wpntVipr 



a, Strawberry guava: b, loquat: c, star apple. These are grown also xld " dUcU1 eatiiei , 



for their ornamental value. (Original.) when the mean tem- 



perature averages about 79.5° F., the Mediterranean fruit fly requires 

 as few as 17 or as many as 33 days to pass through its immature stages. 



