EXTERNAL PARASITES OF BIRDS. 2J5 



The writer's work upon parasitic larvae has been confined to P. 

 avinm. This larva, which is a parasite of the crow, is amply 

 described and figured by Coutant ('15) under the name of P. 

 azurea. The larval period is from ten to thirteen days, and 

 consists of three stages. Larvae measuring from 2 mm. to 15 mm. 

 were found in tli' s of crows. If a third stage larva has not 



attained full -i/e. and cannot obtain food, it will pupate, and the 

 emerging adult \\ill be smaller than usual. 



I'up.il cases belonging to P. avium and P. splctidida collected 

 from the i \cral species of bird- \\ci uilly studied. 



\Vithiu e.n h differences in the pupal cases of the paras 



from different bird IM.MS were observed. Since the adult flies also 

 shou diM inct dil: s, according to the h<t, it seems probable 



that the \ ariations are due to heredity, \\ ith hijji specificity, and 

 not due to the fact that the larva- have led upon different 

 IIOMS. The most noticeable variation in the pupal rases was in 

 the size nd arrangement of spines around the Miv.m il area. The 

 opines in the parasite on the house wrens \\ere .05 mm. long, while 

 in the pupai i.i found in the nest of the scarlet taiia^cr they were SO 

 minute that they seemed like mere stipples. In some the spines 

 .IK inserted diiectly into the underlying ehitin and in others they 

 are on raided ridv -. A more detailed description <,| these host 

 to host variations, with illustrations, is i;i\en in the writer's 

 tlic-is on thi> Mibjcc.1 on file at Cornell t niversity. 



The mi -tliol of hibernation of this p. not known. It 



-((in- moM probabK- that it winters o\ :ii adult. Since the 



- nniM be laid iii new nests in order to hatch in the immedi.ne 

 presence of young n< -i!nu;s, the eggstaj;e i- ruK-d out .is a method 

 of hibernation. < 't the hundreds of pupal cases colli . ted during 

 the fall, \\intcr. and -pring months none \\i-re ali\c. They \\ere 

 either enipt\, or dead and dried up, or p.ir.i-iii/cd by a small 

 hymeiioptenui, of \\hich note will be made later. 



Tin- bird hosts of the North American -pe< ies of the genus 

 rrotocalliph. as follows: 



I. Those obt-er\ ed by the writer: Robin, bluebird, house wren, 

 crow, scarlet tanager, indigo bunting, chipping sparrow, 

 so iii; ,-[)aridw, catbird. 

 II. In addition those listed in the joint paper by R. C. Shannon 



