r 



16 



BULLETIN 640, V. S. DEPARTMENT OF AGRICULTURE. 



the fruit fly can not mature in them. The milk y juice, which exudes 

 copiously from breaks in the skin of the fruits up to the time when 



_ the fruits can be cut 

 for ripening in the 

 house, contains a di- 

 gestive principle that 

 is fatal to the eggs 

 and larvae of the fly. 

 This juice protects 

 the fruits from inf es- 

 tation when imma- 

 ture. But as the 

 fruits become over- 

 ripe, and also unfit 

 for the table, the juice 

 flows less abundantly 

 from breaks in the 

 skin made by the fly 

 when she attempts to 

 lay her eggs, and the 

 eggs which she then 

 lays can mature. As 

 many as 205 flies have 

 been reared from sin- 

 gle overripe fruits. 

 So while the papaya 

 is a host fruit, it is 

 practically never in- 

 fested until too ripe 

 or otherwise unfit for 

 the table. 



AVOCADOS. 



With the exception 

 of one or two early 

 varieties, the infesta- 

 tion of the avocado 

 is so obscure that the 

 general belief prevails 

 in Honolulu that this 

 fruit is free from at- 

 tack. The Guate- 

 mala, or nutmeg, variety is the only one free from attack when growing 

 uninjured. The skin of all other varieties, whether thin or of usual tough- 

 ness, canbe punctured by the adult fly, as proved by many examinations 

 of fruits. The avocado, like the ordinary pear, is best when picked 



Fig. 13.— Avocado. This valuable fruit of California and Florida is 

 subject to infestation in Hawaii. In this instance the maggots are 

 working at the stem and blossom ends. (Authors' illustration.) 



