BIOLOGY OF THE PAPAYA FRUIT FLY. 3 
tached by this process, and the loose seeds in the fruits serve as an 
indication of their presence. When newly born 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 yellow 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 larvae, for they 
do not like the juice of the green fruits and usually 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 larvae, 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 larvse may remain in the fruit for several days after reaching 
maturity. The average time for this stage is 15 days. 
The}' 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 immediately bury 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 only 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 may 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 
