1919] Plath: Larvce of Phormia 377 



There are only two possible explanations in regard to the 

 relation existing between the dead nestlings and the presence 

 of the larvas of Ilylemyia 7iidicola Aldrich. The first is that 

 the young birds died from some cause or other and that the 

 adult flies were then attracted by the odor of the decomposing 

 nestlings to deposit their eggs, or maggots, on them. The 

 second explanation would be that the eggs, or maggots, were 

 deposited on, or near, the young birds while the latter were still 

 alive, the larvae subsequently causing the death of the nestlings 

 by penetrating into their body. It has been known for some 

 time that the larvae of certain species of flies belonging to the 

 genera Hylemyia and Mydaea of the family Anthomyidae 

 attack nestling birds in Central and South America,^ and 

 the second explanation is therefore not an improbable assump- 

 tion. Should further investigations prove that the larvae of 

 Hylemyia Jiidicola Aldrich do attack living nestlings, as now 

 seems probable, then it will be important to determine the 

 range and bring this fly under control if we are not to suffer 

 considerable loss among our wild birds. 



As regards subcutaneous parasitism of nestling birds by 

 fly larvae, I should like to relate an interesting experience I had 

 at Seattle, last summer. During my investigations I came across 

 a nest containing six Willow Goldfinches which were nearly 

 old enough to leave the nest. One of these nestlings had a 

 patch of yellow on its head instead of being of the ordinary 

 color. I turned this bird over to a lady in Seattle to have it 

 reared with a brood of canaries. Two or three days later my 

 attention was called to the fact that some of the feathers on the 

 bird's head were standing up and that the young bird was 

 constantly scratching its head. Upon examining the bird I 

 noticed three small holes, one on top and two at the side of its 

 head. Near the opening of each of these holes the anal end 

 of an active fly larva was visible. The larvae were extracted 

 with considerable difficulty by means of a pair of scissors and 

 forceps, and were about 5 mm. in length and 2 mm. in width. 



® Cf. (1) Townsend, C. H. T., (a) The Grass-quit Bot, an Anthomyiid Parasite 

 of Nestling Birds in Jamaica. Jour. Inst. Jamaica, Vol. II, pp. 173-174. (b) Mydaea 

 spermophilae n. sp. (Larva Parasitic on Nestling Birds). Trans. Amer. Ent. Soc, 

 Vol. XXII, p. 79. (2) Nielsen, J. C, (a) Mydaea anomala Jaenn., a Parasite of 

 South-American Birds. Vidensk. Meddel. fra Dansk Naturhist. Foren. Bd. 63 

 (1912), pp. 195-208. (b) On Some South-American Species of the Genus Mydaea, 

 Parasitic on Birds, ibid. Bd. 65 (1913), pp. 251-256. 



