196 University of California Publications in Zoology [Vol. 19 



kept in a large, narrow-mesh cage and their habits carefully studied. 

 It may be of interest to state that the flies, about 1500, practcially 

 without exception emerged from the pupae between 7 a.m. and 2 p.m. 

 Upon emerging they were of a slightly lighter hue than the adult of 

 our common housefly, Musca domcstiea (Linnaeus), their wings being 

 shriveled up, but .in the course of about an hour or so these straight- 

 ened out and the young flies assumed the dark blue, metallic luster of 

 adult ProtocallipJiora azurea (Fallen). 



Various kinds of food were placed before these flies, such as milk, 

 crushed fruit, cheese, and meat in various forms. The flies readily 

 ate the milk and fruit, especially if the latter was placed on the cage 

 wire instead of the cage floor, but they were rather indifferent to the 

 meat and cheese. Although some of the flies were kept in the cage for 

 sis or seven weeks, none of them, to my knowledge, deposited eggs 

 or maggots. 



It will now perhaps be of interest to zoologists, as well as to bird 

 lovers, to state how frequently the larvae of Protocalliphora azurea 

 (Fallen) were encountered in bird's nests and what effect their blood- 

 sucking habit has on the nestlings. During the eleven weeks in which 

 these experiments were carried on no less than sixty-three nests, 

 representing six species of birds, were examined. Of these, thirty-nine, 

 or nearly two-thirds, were infested by blood-sucking larvae. The 

 accompanying tables will help to illustrate. 



From the first table it will be noticed that birds which build a 

 rather compact nest, as the goldfinches and the linnets, show a con- 

 siderably larger proportion of infection than those which construct 

 nests of a looser texture, as for instance the California brown townee 

 (Pipilo crisaMs crisalis [Vigors]). This may possibly be due to the 

 fact that it is difficult for the fly larvae to keep from falling out of 

 loosely constructed nests. 



All of the 1844 larvae in table 2, excepting the seventy-one indicated 

 by the footnote, were those of Protocalliphora azurea (Fallen). These 

 seventy-one larvae were taken from a linnet nest which contained the 

 skeletons of three young which had been overtaken by death just 

 before they were full fledged. Death had probably been caused by 

 the larvae. When the latter were discovered they were in their 

 pupal stage and were considerably smaller than the larvae of Proto- 

 calliphora azurea (Fallen). All of them had hatched except about a 

 dozen. These unhatched pupae were guarded very carefully, but they 

 all proved to be parasitized by the chalcid fly, Nasonia brevicornis 

 (Girault). 





