BIOLOGY OF THE PAPAYA FRUIT FLY. 7 
usually medium or larger sized, if all sizes are present on the plant. 
They often begin work on a plant when the fruits have just set and 
are very small, and all sizes of fruits are subject to attack. They 
seem, however, to prefer the half -grown or larger fruits, per- 
haps due to a natural instinct, for if the eggs are deposited in a 
nearly mature fruit, the fruit may ripen and decay before the mag- 
gots have completed their growth. On the other hand, if placed in 
very small fruits the maggots will mature before the fruit has 
started to ripen, and they sometimes experience difficulty in escaping 
from green fruits. It has been said that the milky juice from the 
green fruits is fatal to the larvae, but this has not been found to be 
true. In fact, maggots which had been rolled around in the 'juice 
from green fruits completed their development. 
It is not often that an adult fly will oviposit in a fruit where eggs 
or maggots are already present, although in a few instances maggots 
of two distinct sizes were found. When the first ones to mature 
escape they cause the fruit to decay, so the younger ones may not 
be able to complete their development. 
The adult fly alights on the fruit selected and usually walks around 
for a time with a nervous motion. When she has found a suitable 
place she forces her ovipositor through the skin and flesh of the 
fruit and deposits her eggs inside in the seed cavity. This is ac- 
complished by raising the long ovipositor up in a curved position 
and placing the tip of it on the fruit near the end of the abdomen, 
then forcing it through the fruit. The position taken is much the 
same as that of the ichneumon flies in depositing their eggs. 
The eggs are laid in clusters and ordinarily only one cluster will 
be placed in a single fruit, although occasionally two or three are 
found. The fly often stings a fruit several times, as many as 10 
punctures being counted at times, but does not always deposit a 
cluster of eggs. Possibly she is not able to reach through the flesh 
of the fruit in all places and hence withdraws and seeks a new place. 
In fact, many fruits are stung several times and no eggs laid in them. 
This has often happened in the breeding cages where fruits sup- 
posedly containing eggs failed to develop any maggots. Also many 
fruits on the trees have been marked after being stung and no 
larvae ever appeared in them. Usually about two minutes are re- 
quired by the female to deposit the eggs, although instances have 
been noted where the ovipositor remained inserted for an hour or 
more. Occasionally a female will become trapped and die in the 
milky juice which wells up when the skin is punctured. This exu- 
date coagulates and holds the fly if she does not soon escape. When- 
ever a fruit is stung the exudate produces a characteristic mark by 
running clown the side of the fruit and also coagulating in a large 
