206 



winter is prcsuinaljly ])asscd in the egg state. Tlie species is of north- 

 erly (Ustribution in the United States. 



Gnathodus spp. 



The statement in the Twenty-first Rejjort that some sj)(>cies of tliis 

 genus feed on corn is unwarranted. 



PLANT-LICE. 



Aphididce. 



Several root-lice on corn, including the conunon corn root-aphis, 

 were fully treated in the Eighteenth Report of this otlice. The so-called 

 corn leaf-louse, which seems to be more especially a broom-corn and 

 sorghum insect, and the southern grain-louse, which is primarily a 

 wheat insect, haye been discussed as of secondary importance to corn- 

 growers on pages 123-135 of this report. Six other species, ^vhich 

 chiefly infest other plants and whose presence on corn is apparently 

 unusual or accidental, are here briefly mentioned. 



The European (tRain-louse. 



Siphocoryne averue- Vahv. 



This plant-louse (Fig. 216), according to Pergande,* is our common 

 a{)ple-aphis, and is taken also on grains, grasslikc plants, and a few 

 weeds. The broods revert in the fall of alternate years to the ap])le, 

 upon which the sexed intlividuals appear. I'jggs are laid by the ovip- 

 arous females on twigs of apple and related trees and hatch the follow- 

 ing spring. The return migration is completed early in July, after which 

 none of the lice are to be seen on the trees until about September 15, 

 when individuals descended from apple-lice of the i)reyious year migrate 

 to the trees and produce oviparous females. These mature and are 

 then joiiKvl by male migrants. Winged females from corn August 29 

 were pronounced by Mr. IVrgande to be of this species. They are said 

 to be found most frecjuently on wheat. 



The English Grain-louse. 

 Macrosiphum granaria Buckt. 

 (Nedarophora avena>, in part.) 



On two occasions w'inged examjiles of this species (Fig. 217) have 

 been taken on corn, and in one of our large corn l)reeding-cages a small 

 colony of wingless individuals showing the maculation of the abdomen 

 found in this species was observed on the leaves. 



♦Bull. No. 44, N. S., Div. Ent., U. S. Dept. Agr., p. 5. 



