114 



PAPERS ON CEREAL AND FORAGE INSECTS. 



generally been confused with the corn root-aphis, and when found on 

 an}' other plant except Erigeron it has usually been identified as 

 Aphis maidi-radicis. It is much smaller than the latter species and 

 is usually more heavily powdered with a waxy material. Its corni- 

 cles are about one-half the length of those of the corn root-aphis. 

 The third antennal segment in the apterous, viviparous female has a 

 group of 5 or more circular sensoria, and there is also a group of cir- 

 cular sensoria on the fourth, and sometimes also on the fifth segment. 

 In the typical Aphis maidi-radicis these circular sensoria are not 

 present. The winged vivipara are smaller than those of Aphis maidi- 

 radicis, have shorter cornicles, and circular sensoria on the third, 



Fig. 59. — Map showing distribution of Aphis maidi-radicis and Aphis middletoni in the 

 United States. From the records of the Bureau of Entomology. O Localities in which 

 Aphis maidi-radicis has been found or reported on the roots of corn. x Localities in 

 which Aphis maidi-radicis has been reported injurious to asters, p Locality where 

 Aphis maidi-radicis was found on uncultivated plants only. O Localities in which 

 Aphis middletoni has been collected. 



fourth, and fifth antennal segments, while Aphis maidi-radicis has 

 these sensoria only on the third segment. The same differences are 

 found in the oviparous females. 



This species appears to have been a native of the Great Plains, but 

 is noAv distributed widely over the territory east of the Rocky Moun- 

 tains, as is shown in figure 59. 



UNCULTIVATED FOOD PLANTS. 



Aphis middletoni has been found on the following wild food 

 plants: On Erigeron canadensis, mostly in the Northwest; on 

 Erigeron ramosus, in the Carolinas; on the roots of Aster subulatus. 

 at Salisbury, N. C., from May 22 until September 22, 1909, and on 



