38 , _ THE CONDOR | Vol. XXI 
Commenting upon the fact that Protocalliphora azurea is recorded by eol- 
lectors and dipterologists as ‘‘rare’’ or ‘‘very rare’’ and that specimens of this 
fly are only to be found in the larger museums and collections, Coutant correctly 
assumes (loc. cit., pp. 144, 145) “‘that they are not so rare as is generally sup- 
posed, but that the adults are peculiar in their habits, flight, ete., and for this 
reason are rarely taken’’. He then goes on to say (loc. cit., p. 145) : ‘* Few ecol- 
lectors, I imagine, have taken insects very often from the zone of air from fifty 
to one hundred feet above the ground, in the woods; yet from the habits of the 
larvae, this is where we would naturally expect that the adults would oceur’’. 
This is probably correct, but the lower limit, as well as the lateral, will have to 
be extended considerably. Most of the thirty-nine infested nests taken during 
the course of my experiments, as well as the two encountered in 1913, were found 
far distant from forests and all of them came from a height of three to fifteen 
teet above the ground. 
Turning now to the effect which these blood-sucking larvae of Protocalli- 
phoru azurea have on nestling birds, my observations seem to warrant the follow- 
ing conclusions: (1) that from 5 to 10 percent of the parasitized nestlings die 
from loss of blood; (2) that some of the parasitized nestlings which do become 
full-fledged are so weakened by the loss of blood that they fall an easy prey to 
rapacious animals; (3) that the larvae of Protocalliphora chrysorrhea are prob- 
ably more deadly to nestling birds than those of Protocalliphora azurea. The 
jast conclusion seems to be borne out by the case of parasitism recorded by Hen- 
shaw (loc. cit., pp. 87-88), where there was a fatality of nearly 90 percent instead 
of one of only 5 to 10 percent. 
Much remains to be done along this line of investigation in order to determ- 
ine how large and universal the damage is which is wrought on our continent by 
this insect pest. Although the adults of both Protocalliphora azurea and Proto- 
calliphora chrysorrhea are very rarely taken by collectors (cf. Henshaw, loc. cit., 
p. 88; Coutant, loc. cit., pp. 144-145), my investigations prove conclusively that 
the former is not so rare, at. least not in certain parts of the country. So far, 
however, only forty-four birds’ nests, infested by the larvae of one or the other | 
of these flies, have been recorded. All forty-four of these infested nests were 
found at three places, one near Ithaca, N. Y. (Coutant, loc. cit.), two at Welles- 
ley Hills, Mass. (Henshaw, loc. cit.), and the remaining forty-one in the San 
Francisco Bay region. It would be highly interesting, and perhaps for the ben- 
efit of our wild birds, if bird students in other parts of the United States, a& well 
as in Canada and Mexico, would thoroughly investigate this matter in their home 
districts. i 
Massachusetts Institute of Technology, Cambridge, Massachusetts, May 7, 
19TS, 
