FURTHER STUDIES OF THE EMBRYOLOGY OF 

 TOXOPTERA GRAMINUM 



By W. J. Phillips, 



Entomological Assistant, Cereal and Forage Insect Investigations, 



Bureau of Entomology 



In 191 2 the writer, as junior author/ gave in a general way an account 

 of the development of the winter egg of Toxoptera graminum Rondani. 

 This is the first time in this country that the development of the winter 

 egg of any species of Aphididae has been followed out beyond the early 

 stages. It was recognized at the time that there was a wide gap in the 

 continuity of the study of this development, which was not represented 

 by the material then at hand. This paper is intended to supply briefly 

 this missing link. 



A few eggs were collected in the fall of 191 1 and the development was 

 watched carefully in the spring of 191 2. This material gave positive 

 evidence that several links were missing in the data previously obtained. 

 Bulletin no of the Bureau of Entomology was then in press, and it was 

 too late to do more than indicate where the additional data belonged. 

 As the amount of material obtained in 191 1 was rather limited, a large 

 number of eggs were collected in the fall of 191 2 for further study. As 

 previously stated,^ no attempt has been made to treat the subject exhaust- 

 ively, only the main points in the development being considered. 



The same methods of fixation, staining, etc., described in the previous 

 paper ^ were employed. 



Turning to Plate VII of Bulletin no, one will readily see that the gap 

 previously referred to occurs between figures i and 2, where the polar 

 organ is entirely lost track of after figure i. It is also at this point in 

 the development of the embryo that the revolution occurs; hence, there 

 is not a single figure in the first publication to illustrate the revolution 

 of the embryo and the fate of the polar organ. 



The polar organ is a unique, newly discovered body, since, so far as 

 the author's information goes, no other observer has heretofore figured 

 any such body; and, while it was exceedingly unfortunate that figures 

 illustrating its fate and the revolution of the embryo could not then be 

 supplied, this serious defect is now eliminated. In view of the neces- 

 sarily incomplete Plate VII of Bulletin no, it has been thought best to 

 make an entirely new series of figures covering the same period of devel- 

 opment as that covered by Plate VII, drawn from a new series of sections, 



1 Webster, F. M., and Phillips, W. J. The spring grain aphis or "green bug." U. S. Dept. Agr. Bur. 

 Ent. Bui. no, 153 p., 48 fig., 4 diagr., 9 pi. 1912. 



2 Id., p. 94. 

 ' Id., p. 9S. 



Journal of Agricultural Research, Vol. IV, No. s 



Dept. of Agriculture, Washington, D. C. Aug. 16, 1915 



K— 20 

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