1909] Toxoptera graminum and its Parasites 73 



occurrence of Toxoptera in any considerable section of the country 

 cannot be due to a lack of uncultivated food plants. Mr. Phil- 

 lips found that the species readily developed on the following 

 plants in his breeding cages: Dactyhs glomeraia, Eleusine indica, 

 Eragrostis pilosa, E. megastachya, Sporobolus neglectiis, Agropyron 

 sps., Elymus virginiciis, E. canadensis and Bromus secalinus. 



SEASONAL HISTORY. 



Though in the main following quite closely the developmental 

 habits of other Aphids, this species exhibits some striking con- 

 trasts. While it probably passes the winter in the egg state in 

 the northern portions of the country, it is quite certain that it is 

 not restricted to that mode of hibernation during mild winters, 

 or in the South. The fact that viviparous 9 9 (f^gs- i, 2) 

 sent from Leavenworth, Kansas to Washington, D. C, in March, 

 and there placed indoors, produced oviparous ? 9 (fig. 3) and 

 c? c? (fig. 4) in April, and, in case of the latter, even till May 18, 

 shows that the sexes may occur in spring. As information on 

 the occurrence of the sexual forms appears to be entirely lacking 

 in the South, it would be too much to connect the presence of 

 these forms in spring as showing a changed summer condition 

 in the South, whereby the dry season instead of the winter 

 might be passed in the egg. Bearing upon this point, but prov- 

 ing nothing unfortunately, it may be stated that at Richmond, 

 Indiana, in the autumn of 1907, Mr. Phillips encountered a 

 pronounced lack of oviparous 9 9 , the weather being unusually 

 wet. During a corresponding period of 1908, with one of the 

 severest droughts on record prevailing at the time, he was unable 

 to get a sufficient number of viviparous- 

 9 9 to keep up his experiments, while 

 the sexual forms were present in abun- 

 dance. 



Two of my assistants, Mr. W. J. 

 Phillips, and Mr. C. N. Ainslie, have on 

 occasions dissected 9 9 and found both 

 eggs and embryos in the ovaries, the 

 latter in spring; while the former, in 

 the fall, observed in one instance that t. „ ^ • 



^ . ., , , riG. 3 — bprmg grain-aphis 



the eggs were m one side and the em- {Toxoptera graminum): Ovi- 



bryos in the other side of the abdomen, Parous female with eggs in 



,1 - ^ . . body, greatly enlarged; at 



as though one ovary had produced right, egg still more enlarged. 



eggs and the other embryos. (Ongmai.) 



