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ENTOMOLOGICAL SOCIETY 



it under the microscope, the Lysiphlebus larva was observed to 

 work its way actively about as shown by the accompanying 

 figures (PI. VI), these movements being always forward and 

 easily observed through the skin of the victim until this had 

 become too opaque and the movements of the parasite larva 

 too slow to detect. When these observations began, the move- 

 ments of the parasite larva were accompanied, on the part of 

 the victim, by a clutching of the leaf and a rigidity of the 

 muscles of the limbs, and it is probable that the pain brought 

 about by these movements led to the death grasp of the aphis, 

 thus accounting for the tenacity with which the dead and dried 

 empty skins of parasitized aphides remain attached to leaves 

 and other objects to which the dying host has attached herself, 

 long after the adult parasite has made its escape. 



Taking up these observations in detail, fig. i (PI. VI) shows 

 the host as when first placed under the microscope at ii 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 para- 

 site larva within her body. Between ii a. m. and ii 135 a. m. 

 the Lysiphlebus 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 shown by 

 figs. 2-7, Plate VI. Between 1 1 135 and 

 1 1 140 a. m. the larva had completed another 

 revolution, probably the fourth from the 

 beginning. The fifth revolution was com- 

 pleted at 1 1 :50 a. m., and the sixth at 11 :58 

 a. m., while the seventh was completed by 

 12:07 P- ''•''• With the eighth revolution, 

 shown by figs. 8 and 9, completed at 12:11 

 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 rotation had 

 been completed (fig. 10) and the larva had 

 decidedly contracted. Fig. 11 shows the 

 situation of both larva and pupal envelope at 

 12:20; fig. 12, at 12:22; fig. 13, at 12:27; 

 fig. 14, at 12:32; and fig. 15, at 12:32^4 p. 

 m. At 12:35 P- "^- there were apparent on 

 the body of the parasite larva small, roundish cells of a yellow 

 color. By this time the skin of the host had reached the semi- 

 globular, typical form, which did not materially change after- 

 ward, though a slight movement in the larva could be detected 



Fig. 4. — Unusual 

 position of larva of 

 Lysiplilebus tritici in 

 body of Toxoptera 

 graminum. (Drawing 

 made for Bureau of 

 Entomology and pub- 

 lished by permission 

 of the Secretary of 

 Agriculture.) 



