infested fields. The species that have been most conspicuous in this 

 work are Goccinella 9-notata Hbst., C. sanguinea L., Hippodamia paren- 

 thesis Say, and H. convergens Guer. (fig. 3). Megilla maculatn DeG. 

 is rarely seen with the preceding in infested fields. 



Of the hymenopterous parasites J.ysiphlehus frifici Ashm. is especially 

 useful.- In southern Indiana, in 1890, this little slender, black, four- 

 winged fly became excessively abundant and destro3'ed myriads of the 

 pest. When at work this diminutive enem}' of these aphides may be 

 seen running over the plants, thrusting its ovipositor into their bodies. 

 Soon thereafter the body of the parasitized aphis becomes swollen and 

 rounded, and at the same time the skin hardens and changes in color 

 to a leather-brown. Shortly after, a circular disk is cut by the parasite 

 in the body wall of its host, and pushing this out the fully developed 



Fig. S.— Hippodamia converoenn, a lady beetle which devours the spring grain-aphis: 

 a, adult; h, pupa; c, larva. All much enlarged (from Chittenden). 



insect makes its way forth to at once begin laying eggs in the bodies 

 of others of its host, both old and young. In southern Indiana, in 

 1890, these parasitized individuals became so abundant on the leaves 

 of the grain as to add materially to the brown color due to the effects 

 of their own feeding on the plants, and their presence could be noted 

 from a considerable distance. Prof. E. Dwight Sanderson, while at the 

 Texas Experiment Station, came to the conclusion that in Texas the 

 natural enemies ordinarily destroy such large numbers of this pest that 

 it is held in check thereby. The writer came to a similar conclusion 

 manj^ 3"ears ago, and concluded, further, that the abundance of these 

 parasites throughout the area in which this aphis is destructive is pri- 

 marily regulated by the weather during the time intervening between 

 November and Ma3\ 



METEOKOLOdlCAI. INFLUENCES. 



Attention has already been called to the fact that the spring gi'ain- 

 aphis can breed in the fields during the prevalence of a temperature 

 that would render most insects inactive. It seems almost equally clear 

 that serious and widespread outbreaks of this insect are due to a lack 



