1909] Toxoptera graminum and its Parasites 83 



Wash., Vol. IX, p. III.) Later observations by Mr. Kelly on the 

 movement of the parasitic larva, made from beneath and after 

 the dorsal skin of the host had become too opaque to continue 

 them from above, shows that the ventral skin of the Toxoptera 

 splits and the slit thus formed widens, as the skin assumes a ro- 

 tund shape, until it becomes nearly circular. The parasite larva 

 spins a cocoon of silken threads within the empty skin of its host, 

 and, by reason of this disc-like hole in the ventral surface of the 

 host skin, attaches the whole structure firmly to the surface of the 

 leaf. 



Taking up these observations in detail, figure i of plate XIV 

 shows the host as wdien first placed under the microscope at 11 

 A. M., while she was still alive and at a time when she seemed to 

 tighten her grasp on the leaf with each movement of the parasite 

 larva within her body. Between 11 a. m, and 11:35 ^- m. the 

 Lysiphlehus larva had made three complete revolutions in the 

 body of its host, some of the different positions assumed, as also 

 the gradual shaping of the skin of the now dead Toxoptera being- 

 illustrated by figs. 2-7 in the plate. Between 1 1 :35 and 1 1 40 a. m., 

 the larva had completed another revolution, probably the fourth 

 from the beginning. The fifth revolution was completed by 

 II 130 A. M., and the sixth at 11 :58 a. m., w^hile the seventh was 

 completed by 12 107 p. m. With the eighth revolution, shown by 

 figs. 8 and 9, completed at 12 :ii p. m., the skin of the host insect 

 had been brought into its rotund shape and the larva had just 

 begun to contract preparatory to pupation. At 12:15 the ninth 



EXPLANATION OF PLATE XIV. 



Fig. 1 — Position of larva of Lysiphlehus tritici in body of wingless adult 9 

 of Toxoptera graminum, just before beginning its revolutions for fashioning the 

 body of the Toxoptera into a pupal envelope, 11a. m. 



Figs. 2-7. — Some of the positions assumed by the Lysiphlehus larva 

 between 11a. m. and 11 :,35 a. m,, during which time it made three complete 

 revolutions. 



Figs. 8, 9. — Positions during and at completion of eighth revolution, 12:11 



P. M. 



Fig. 10. — Position at completion of ninth revolution, showing contraction 

 of the larva, 12.15 p. m. 



Fig. 11. — Position at 12:20 p. m. 

 Fig. 12. — Position at 12:22 p. m. 

 Fig. 1.3. — Position at 12:27 p. m. 

 Fig. 14. — Position at 12:32 p. m. 

 Fig. 15. — Position at 12:32* p. m. 



