1909] Toxoptera graminum and its Parasites 81 



Some studies were made of the final larval stage by Miss 

 Weeks, of Manhattan, Kansas, under my supervision, the results 

 of which were given in brief by me at the 

 first meeting of this Society in Boston, 

 and are as follows:* 



A wingless 9 of T. gramimim w^as 

 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 oviposi- 

 tion by the Lysiphlcbns, the larva being 

 at the time quite full grown and occupy- /'«•. 8— Wingless female 



^ . . . , . 01 spring gram-aphis, con- 



mg its normal position in the posterior taining larva of the par- 

 part of the abdomen of the host insect, ^site Lysiphlcbus tritici. 



i-, „ , 1 , 11 1 Much enlarged (original). 



From all that we have been able to learn 



the very young parasite larva takes this position, and, refraining 

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

 in contact with or injure any vital organ of its host, the effect 

 being to reduce the period of reproduction of the 9 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 9 Toxoptera from the field and placing it under 

 the microscope, the Lysiphlehiis larva was obser\-ed to work its 

 way actively about as shown by the accompanying plate, these 

 movements being always forward and easily observed through 

 the skin of the victim until this had become too opaque. The 

 movements 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. But it has since been learned that this rigor mortis 

 has little if anything to do with the adherence of the cocoon to 

 the leaf surface, as was previously supposed by me, except per- 

 haps to temporarily hold the body of the aphid fast until the 

 parasite larva can anchor it more securely. (See Proc. Ent. Soc. 



* These observations were afterwards published in Proc. Ent. Soc. Wash. 

 Vol. IX, Nos. 1-4, pp. 110-113, Plate VI. 



