1912} Mediterranean Fruit Flies 403 
the mountains rise very abruptly but in general the slope is 
quite gradual. The bottom of the valley consists largely of 
taro patches, (Pl. XXX). 
At the head end of the valley, in a circle about a half mile in 
diameter, fifty kerosene traps were wired among the branches 
of citrus, fig, guava, hau and tropical almond trees. In a 
previous experiment we found that of every thousand Medit- 
erranean fruit flies captured in kerosene only three were females 
and for this reason only marked males were used. 
£23 
Fig. 2. Kerosene trap wired to a branch of a lemon tree. The white enameled 
pan containing the oil is covered with a galvanized iron cover to keep out the rain. 
The fruit flies enter the trap in the space between the cover and the rim of the pan. 
The Mediterranean fruit flies were set free in lots containing 
from two to six hundred specimens. When the first lot of flies 
were set free, the jars containing the marked individuals were 
