July 9, 1917 



Study 0} Eriosoma pyricola 



73 



they were somewhat darker in color — the newly bom larvae of the pear- 

 root aphis. 



In confinement it was found that 12 spring migrants deposited an 

 average complement of 22 young with a range of from 10 to 39. These 

 were in every case deposited within three days, and in most cases within 

 24 hours of transforming 



Root-feeding generations were bred m the laboratory at Walnut 

 Creek, Cal., from the wingless progeny of the spring migrants, and in 

 due course the third and fourth generations yielded a large percentage 

 of fall migrants. These fall sexuparous migrants were bred contempo- 

 raneously with others which came from a root-feeding strain originally 

 started in 1915. 



It may be said that the young deposited by the spring migrants readily 

 fed on pear stocks of Kiefifer, French, and Japanese varieties, but, like 

 the root-dwelling larvae, absolutely refused to feed upon apple roots and 

 fed only in very rare instances upon roots of the quince. 



The readiness exhibited by the migrant progeny to settle on pear 

 roots was taken advantage of in colonizing a series of young orchard 

 trees for the purpose of later insecticide tests, and elm galls containing 

 migrants and pupae were buried near the roots in the soil with the result 

 that in 75 per cent of the trees root infestation speedily resulted. This 

 was found to be a much handier method of general colonization than the 

 use of pieces of infested roots or the application of individuals by brush. 



A diagram of the complete life cycle of E. pyricola is given in 

 figure I. 



Fjg. I. — Eiaeram shewing the 3:ic cxcic cf Er.^ioma pyruida. 



LITERATURE CITED 

 (i) Baker, A. C. 



1916. IDENTITY OF ERIOSOMA PYRi. 7n Jour. Agr. Research, v. 5, no. 23, p. 

 1115-1119, I fig. 



(2) and Davidson, W. M. 



1916. WOOLLY PEAR APHIS, hi Jour. Agt. Research, v. 6, no. 10, p. 351-360, 

 I fig. 



