OF WASHINGTON. Ill 



Stage underground, however, rarely do more than work their 

 bodies about until an earthen cell is formed, which is sometimes 

 lined with silk, but in the Coleoptera even this is generally 

 omitted. In all cases — at least so far as the author can call to 

 mind — the cavity within which the transformation is to take 

 place is the final work of, and is shaped by the movements of 

 the fully developed larva. 



That many of the internal parasites of Aphididse pass their 

 entire life cycle within the bodies of their hosts, the adults 

 emerging from the dead and dried bodies of their victims, is 

 well known. The peculiar rounded form taken on by a para- 

 sitized aphis after life has become extinct is also a matter of 

 common observation, and, indeed, these nearly globular, brown 

 corpses are usually to be expected wherever there are great 

 numbers of aphides collected together, as with our grain-infest- 

 ing species. 



No one, it appears, has taken pains to observe the process of 

 fashioning this pseudococoon by the parasite larva, whose 

 habits in this respect do not differ materially from those of 

 other insects, except in so far as is made necessary by the ma- 

 terial used by the constructor. 



The observations and drawings which form the basis of this 

 paper were made with material furnished by and under the 

 direction of the author by Miss E. Weeks, at Manhattan, Kans., 

 in connection with investigations of T ox opt era graminum 

 Rond. and its parasite, Lysiphlcbus tritici. The living adult 

 wingless female of T. graniinum was taken from the field when 

 beginning to take on the yellowish color which first denotes 

 parasitism, and which precedes the amber color of the more 

 advanced stage. Evidently this was on or about the sixth day 

 from the time of oviposition by the Lysiphlebus, the larva 

 being at the time quite full grown and occupying its normal 

 position in the posterior part of the abdomen of the host insect 

 (see Plate VI, fig. i ) . From all that we have been able to learn, 

 the very young parasite larva takes this position, and, refrain- 

 ing from moving about to any considerable degree, it does not 

 come in contact with or injure any vital organ of its host, the ef- 

 fect being to reduce the period of reproduction of the Toxoptera 

 to a very few days at most. But on reaching its full larval 

 development, it seems suddenly to become more active, and 

 with its first extended travels within the abdomen of its victim 

 the last spark of life remaining in the latter is extinguished. 

 It was just at this point that the observations herein recorded 

 were made. 



On bringing the female Toxoptera from the field and placing 



