BIOLOGY OF THE PAPAYA FEUIT FLY. 3 



tached by this process, and the loose seeds in the fruits serve as an 

 indication of their presence. When newly bom the maggots are 

 almost transparent, but soon assume a shining, dirty white color 

 while in the seed cavity. Later on, as they continue to develop, they 

 eat into the flesh of the fruit, first close to the cavity and then work- 

 ing farther out until, when mature, they are close to the skin. They 

 have then only to eat a hole through the rind to escape. During this 

 latter part of their life they become a rich golden j^ellow color, like 

 the color of the fruit on which they are feeding. The presence of 

 the maggots in the fruit usually causes it to turn yellow and ripen 

 prematurely. This is a distinct advantage to the larvse, for they 

 do not like the juice of the green fruits and usuallj^ remain around 

 the seed cavity until the flesh begins to soften. 



The mature maggots (PL I, C, a) average about 11 mm. in length, 

 are subcylindrical in shape, and taper anteriorly to the mouth. 



The length of time required for their development varied from 10 

 to 27 days in a large number of tests. The cooler weather of winter 

 prolongs somewhat the length of the larval stage. Conditions un- 

 favorable to the larv83, such as the fruit decaying or the maggots be- 

 ing removed from the fruit, will cause them to transform before the 

 normal time. On the other hand, if the conditions are favorable 

 the larvae may remain in the fruit for several days after reaching 

 maturity. The average time for this stage is 15 days. 



They make their escape by eating a hole through the skin and drop- 

 ping to the ground. As a rule, when one escapes the others will 

 follow in rapid succession, and often all emerge from the same exit 

 hole. If the fruit has already fallen from the tree the maggots go 

 into the ground immediately under it ; if the fruit is still on the tree 

 they drop to the ground. Often a larva will remain partly emerged 

 from a fruit and continue a wriggling, twisting motion for an hour 

 or more before finally dropping. When once on the ground the 

 maggots immediatel}^ bur}^ themselves and never wander around on 

 the soil. The transformation is completed within a few hours after 

 entering the ground. The period of exposure from the time of leav- 

 ing the fruit to entering the soil ordinarily would be onh^ a minute 

 or two, and consequently there would be little chance for parasitism 

 here. Very rarely a maggot will pupate inside a fruit. 



The number of maggots in a single infested fruit sometimes runs 

 up as high as 40, although ordinarily there are about 15 or 20. A 

 very small fruit msLj have only 2 or 3. 



If confined in breeding jars where no soil is present the larvae 

 usually will not pupate. In a glass stender dish or Petri dish the 

 mature maggots would remain in the larval stage for three or four 

 days, continually crawling around the dish. After several days they 



