8 oo 
Journal of Agricultural Research 
Vol. V t No. 17 
a flow of this staining fluid. Data on file show that practically all punc¬ 
tures made by female fruit flies in host fruits, the epidermis of which does 
not emit fluid detrimental to the pest from one or several standpoints, 
contain eggs, but no punctures or eggs have ever been found by the 
writers in the peel of bananas growing under normal field conditions and 
suitable for the export trade. This is true in spite of the fact that many 
thousand fruits have been examined. 
One of the most severe tests to which any fruit can be subjected to 
determine whether it can support the fruit fly is to confine it closely with 
several hundred fruit flies of both sexes. Yet even under this extreme 
and unnatural condition only 1 egg was laid in 1,449 bananas exposed 
while still attached to the tree, and that was killed, presumably by the 
tannic acid in the peel. While 22 eggs were deposited in 1,145 more 
mature fruits, also attached to the tree, some of which were too mature 
for export trade, these eggs, or the larvae hatching from them, died within 
the peel. When one realizes that many thousand eggs have been secured 
by the writers under like conditions in preferred hosts, it is clear that 
adult fruit flies find it extremely difficult to oviposit in fruits on the tree 
even under forced conditions, both when the fruit is sufficiently mature 
for shipment and for a period of at least nine days thereafter. At the 
end of this period it is considered too mature to stand transportation to 
the mainland. And inasmuch as shippers are paid by the bunch for their 
fruit, the banana markers in Hawaii are likely to mark bananas for 
cutting that are slightly greener than necessary in order to safeguard 
against unforeseen delays in shipment and crowded conditions on board 
the steamer which hasten the ripening process. 
The difficulty experienced by the female Mediterranean fruit flies in 
ovipositing in green though mature fruit still attached to the tree is 
undoubtedly a mechanical one. She no sooner ruptures the epidermis 
in her attempt to form a cavity within which to deposit her eggs than she is 
literally forced away from her position by the exuding sap. It is possible 
that repeated attempts at oviposition, which are known to occur in other 
host fruits under natural conditions, may account for the 7 instances out 
of the 494 under forced or abnormal conditions when females were suc¬ 
cessful in depositing eggs. That the immunity enjoyed by Chinese and 
Bluefield bananas up to the time they are ready for shipment and for a 
period of at least nine days thereafter is due to the copious supply of sap 
is still further emphasized by the ease with which they become infested 
under similar forced conditions, or outdoor conditions, when the fruit has 
been cut for a short time. Fruit cut from the tree or from the bunch 
bleeds at the point where severed. The pressure of sap within is at once 
reduced and the amount of sap that exudes from cuts in the peel decreases 
until but little exudes after the fruit has been cut for several days. The 
data giving the results of close confinement of flies with bananas after 
they have been cut for shipment show that while the females have diffi- 
