6 BULLETIX 992, TJ. S. DEPARTMENT OF AGRICULTURE. 
punctured nuts and females were observed frequently to visit these 
nuts, where copulation and oviposition took place. In approaching 
these nuts the females usually came by easy stages, flying and crawl- 
ing near the nut before alighting upon it. When the male would 
observe a female approaching he would become much excited, moving 
back and forth, whirling around, and raising and lowering the wings 
in rapid succession, but remaining near the puncture made with the 
nail point. On the arrival of the female upon the nut the male 
would usually back away from the nail puncture a short distance 
and there remain stationary, with wings elevated above the back, 
watching the female intently. When the female would find the 
puncture and start to insert the tip of her abdomen into the opening 
for the purpose of depositing eggs, the male would spring upon her 
and copulation would take place. There would then follow alter- 
nating periods of oviposition and copulation, the male sometimes 
continuing mounted while oviposition was in progress, and sometimes 
dismounting but remaining near by. (PI. III. d.) Frequently there 
would be four or five periods of each before the female would fly 
away. After this procedure the male was likely to continue on 
guard at the same place, for the nail pricks were visited frequently 
by ovipositing females. 
The flies were observed to be much more abundant on the lower 
than on the higher branches of trees, and there was a great differ- 
ence in the numbers of flies on individual trees of the same species. 
On a group of heavy-laden Persian walnut trees of the variety 
known as Hall, at West Willow. Pa., it was estimated that one fly 
was present for every two nuts on the trees. The variation in the 
numbers of flies on' individual trees was followed by a corresponding 
abundance or scarcity of maggots in the nuts of each. 
Flies were observed to feed upon the juice that flowed from ovi- 
position scars and upon the naturally more or less gummy surface 
of the nuts. In feeding they would eject from the mouth a particle 
of clear liquid onto the surface and after working it over with the 
purselike, external mouthparts would swallow it again. 
NATURE OF INJURY.* 
In native black walnuts the eggs of the husk-maggot fly are 
usually deposited so late in the season that the resultant maggots 
do not prevent the nuts from maturing and dropping normally. 
Thus, while apparently all the eggs are laid in nuts on the trees. 
the development of the maggots and the blackening of the husks 
which results from their feeding take place chiefly in fallen nuts. 
In Persian walnuts, however, eggs appear to be laid earlier in the 
development of the nuts. Bearing trees were observed in Maryland 
and Pennsylvania, a short time before the crop had ripened, on which 
