404 Annals Entomological Society of America [Vol. V, 
held on a level with the eye to better enable the observer to 
note the direction of flight. In order to arouse the flies into 
activity and hasten their departure, the sides of the jars were 
snapped lightly with the fingers, with other lots, however, the 
jars were placed upon the ground and the males were allowed 
to escape. With the sky as a background, the unaided eye 
could follow the insects in their flight to a distance of about a 
hundred feet, but with the use of a field glass, the flies could be 
followed to a much greater distance. 
While liberating the first lot of five hundred fruit flies in the 
center of the circle of traps it was observed that the wind played 
an important part in their direction of flight. A heavy north- 
east wind was blowing from the mountains to the sea, while 
these marked diptera were liberated, and it was striking to note 
that they flew and were carried with the wind down the valley 
with extreme rapidity towards the city of Honolulu. Since 
the prevailing winds at this time of the year are from the north- 
east, a change in the arrangement of the traps was made. The 
traps that had been located in that half of the circle nearest the 
head end of the valley, were placed amongst the trees of two 
citrus grooves, (Pl. XXX, 4), situated on the leeward side of 
the remaining semicircle of traps. (Pl. XXX, white line.) 
The trypetids were liberated from three different points. 
As was already mentioned five hundred fruit flies with the hind 
leg cut, were liberated in the center of the circle of traps, about 
a half mile in diameter. After the traps had been rearranged 
a thousand specimens with the front leg severed were set free 
from the head end of the valley about a half mile from the traps. 
Five hundred males with the middle leg amputated were freed 
at the head end of the valley from the side of a mountain at an 
elevation of about three hundred fifty feet and at a distance of 
about one mile from the traps. A glance at the photograph 
shows the three points of liberation. _ (Pl. XXX, 1, 2, and 3). 
The orientation of the marked individuals was carefully 
noted with the liberation of each lot of flies under the different 
climatic conditions. Whenever a heavy or light north-east 
wind blew from the mountains to the sea, the insects as soon as 
liberated would orient themselves with the wind and fly down 
the valley but when a south-west wind from the sea to the 
mountains prevailed, the specimens again oriented themselves 
