198 University of California Publications in Zoology [Vol.19 



when I approached the nest. Nearly all of the fly larvae found in 

 this nest showed traces of fresh blood. 



As far as I am able to ascertain, there are only two cases of blood- 

 sucking fly larvae on record for the United States. In 1908 Henshaw 

 recorded the infestation of two successive broods of bluebirds. Sialia 

 sialis (Linnaeus), by the larvae of Protocalliphora chrysorrhea 

 Meigen), 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 warning about the danger of this 

 insect pest to our native birds. 



Seven years later Coutant (1915). while studying blood parasites 

 of the common crow (Corvus brachyrhynchos Brehm) at the Bio- 

 logical Laboratory of Cornell University, came across some larvae of 

 Protocalliphora azurca (Fallen). Most of his deductions, based upon 

 the study (if these larvae, agree with my observations. However, his 

 conclusion (p. 139) that "the larvae prefer rather dry places to moist 

 ones and are therefore not accustomed to living in decomposing or 

 fecal material" and that (p. 143) "the larvae when ready to trans- 

 form, apparently leave the more occupied parts of the nest in the 

 vicinity of their food-supply and seek a dry . . . portion" of the nest. 

 were not borne out by my observations and experiments. In all cases 

 the larvae preferred the moist fecal material and pupated in it. This 

 discrepancy between Coutant 's results and mine is undoubtedly due 

 to the fact that 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. 



Commenting upon the fact that Protocalliphora azurca (Fallen) 

 are recorded by collectors 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 (1915. pp. 144. 145) correctly 

 assumes "that they are not so rare as is'generally supposed, but that 

 the adults are peculiar in their habits, flight, etc.. and for this reason 

 are rarely taken." He then jroes on to say I p. 145) : "Few collectors. 

 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 occur." This may be partly correct, but the lower limit 

 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 



