THE PREVALENCE OF PHORMIA AZUREA FALLEN 



(LARVA PARASITIC ON NESTLING BIRDS) IN THE 



PUGET SOUND REGION AND DATA ON TWO 



UNDESCRIBED FLIES OF SIMILAR HABIT. 



By O. E. Plath. 



(Together with Descriptions of the Two New Flies by 

 C. H. T. TowNSEND and J. M. Aldrich.) 



In two recent papers^ the writer pointed out that the larvae of 

 Phormia- aziirea Fallen habitually suck the blood of nestling birds, 

 sometimes with fatal results, and that the adult flies, contrary 

 to the opinion of most dipterists, are quite abundant, at least 

 in the San Francisco Bay Region. Last summer (1918), while 

 visiting Seattle, he had occasion to ascertain whether Phormia 

 azurea Fallen also occurs in the Puget Sound Region and found 

 that it is as frequent there as in the San Francisco Bay Region. 

 During his stay at Seattle (June 15th to August 1st), fifty-four 

 birds' nests were examined containing nestlings belonging to ten 

 different species of birds. Of these fifty-four nests, thirty-three 

 were infested by the larvae of Phormia azurea Fallen,^ one 

 by those of a new species of Phormia, and six by those of a 

 new fly belonging to the genus Hylemyia of the family Antho- 

 myidae. Drs. J. M. Aldrich and C. H. T. Townsend, of the United 

 States Bureau of Entomology, have been kind enough to 

 describe the two new flies, the descriptions being appended to 

 this paper, and the two flies will hereafter be referred to as 



1 Plath, O. E. (a) Parasitism of Nestling Birds by Fly Larvae. The Condor, 

 Vol. XXI (1919), pp. 30-39. (b) A Muscid Larva of the San Francisco Bay Region 

 which Sucks the Blood of Nestling Birds. Univ. Calif. Publ. Zool., Vol. XIX 

 (1919), pp. 191-200. 



2 A synonym of ProtocaUiphora which Dr. C. H. T. Townsend of the United 

 States Bureau of Entomology considers more appropriate. 



3 A large number of specimens of this fly were sent to Dr. C. H. T. Townsend 

 of the United States Bureau of Entomology who has informed me that the fly was 

 correctly identified bv Mr. C. W. Johnson (Cf. a. The Condor, Vol. XXI, p. 34. 

 b. Univ. Calif. Publ. Zool., Vol. XIX, p. 194. Dr. Townsend has also called my 

 attention to the fact that Coutant's fly (Cf. Coutant, A. F., The Habits, Life 

 History, and Structure of a Blood-sucking Muscid Larva {ProtocaUiphora Azurea). 

 Jour. Parasit., Vol. I, pp. 13.5-150) is not ProtocaUiphora {Phormia) azurea Fallen, 

 as was claimed by Coutant, but Phormia chrysorrhea Meigen. This fact. Dr. Town- 

 send thinks, may account for the disparity between Coutant's observations and 

 mine (Cf. The Condor, Vol. XXI, p. 37. b. Univ. Calif. Publ. Zool., Vol. XIX, 

 pp. 198-199). 



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