Jan., 1919 PARASITISM OF NESTLING BIRDS BY FLY LARVAE 37 
taet that it is difficult for the fly larvae to keep from falling out of loosely con- 
structed nests. 
All of the 1844 larvae in Table II, excepting the seventy-one indicated by the 
starred foot-note, were those of Protocallizhora azurea. These seventy-one lar- 
vae were taken from a linnet nest which contained the skeletons of three young 
which had been overtaken by death just before they became full-fledged. Death 
had undoubtedly been caused by the larvae. When the latter were discovered, 
they were in their pupal stage and were considerably smaller than the larvae of 
Prolocalliphora azurea. All of them, excepting about a dozen, had hatched. 
These unhatched pupae were guarded very carefully, but they all proved to be 
parasitized by Nasonia brevicorna. 
The death of six other nestlings, including the four which had died in 1913, 
could be traced with more or less certainty to the Muscid larvae, as in the case 
of the three linnets whose skeletons I found, and the two goldfinches used for 
experimenting. One of these nestlings, a nearly full-fledged California Lin- 
net, was discovered when it had been dead only a short time. A number of the 
Protocalliphora larvae had actually penetrated into its body. The nest in which 
this dead bird was found contained another nestling of the same brood. Though 
apparently rather weak, this nestling took wing when I approached the nest. 
Nearly all of the fly larvae found in this nest showed traces of fresh blood. 
It was not until after I had completed my investigations that my attention 
was called to two articles concerning blood-sucking fly larvae’. As far as I am 
able to ascertain, these are the only two instances of blood-sucking fly larvae on 
record as far as North America is concerned. In the second of these two articles 
Coutant mentions four papers (those by Dufour, Du Buysson, Rouband, and 
Rodhain) concerning blood-sucking fly larvae in Africa, South America, and 
Europe, but neither the Harvard University Library nor the Boston Public 
Library contain any of these four articles. 
In 1908 Henshaw (loc. cit.) recorded the infestation of two successive broods 
of Bluebirds (Sialia sialis) by the larvae of Protocallaphora chrysorrhea (Mei- 
gen), which had been reported to him by Mrs. Emma F. Everett, of Wellesley 
Hills, Massachusetts. These two cases of parasitism were decidedly fatal, seven 
out of the eight nestlings dying as a result. Henshaw closes with a note of warn- 
ing about the danger of this insect pest to our native birds. 
Seven years later Coutant (loc. cit.), while studying blood parasites of the 
Common Crow (Corvus brachyrhynchos) at the Biological Laboratory of Cornell 
University, came across some larvae of Protocalliphora azurea. Most of his de- 
ductions, based upon the study of these larvae, are well founded. His conclu- 
sion however (loc. cit., p. 139) that ‘‘the larvae prefer rather dry places to moist 
ones and are therefore not accustomed to living in decomposing or fecal mate- 
rial’’ and that (loc. cit., p. 148) ‘‘the larvae when ready to transform, apparent- 
ly leave the more occupied parts of the nest in the vicinity of their food-supply 
and seekadry . . . portion’’ of the nest, were not borne out by my observa- 
tions and experiments. In all cases the larvae preferred the moist faecal material 
and pupated in it. This discrepancy between Mr. Coutant’s results and mine is 
undoubtedly due to the fact that Mr. Coutant based his conclusions upon the 
study of a comparatively few larvae, and that even these few were not studied 
by him in their natural environment, the bird’s nest. 
ig. Henshaw, H. W. A Parasitic Fly Injurious to our Native Birds. The Auk, xxv, 
190%, pp. $7-88. b. Coutant, Albert F. The Habits, Life History, and Structure of a 
Blood-sucking Muscid Larvae (Protocalliphora Azurea), Journal of Parasitology, vol. I, 1915, 
pp. 135-150. 
