CONTRIBUTIONS OM THE CORN BOOT-APHIS. 1 1 .' j 



living lice from the different plants. Armoracea we nave found very abundant 

 here on horse-radish. 



As very complete descriptions of the different form- of Aphis 

 maidi-radicis have been published, no descriptions are given in this 



paper except that of the winged male, which has not been before ob- 

 served or described. Two of these male- appeared in the vials in 

 which Aphis maidi-radicis from the roots of Ambrosia artemisii folia 



were being reared on corn, and one in the vial of Aphis from Lep- 

 tochloa -filiform I*. Two of these were used in experiments: the other 

 was preserved and is described below. 



Winged $ (fig. 58). — Head, thorax, eyes, and appendages black. Abdomen 

 green, with dark transverse bars on the dorsal side of the 5th, Gth. and 7th 

 somites. The beak reaches the metathorax. The antennae reach the caudal 

 end of the second abdominal somite. The circular sensoria are arranged od 

 the antenna as follows: 24 on the third. 12 on the fourth. 7 <>n the fifth, 4 on 

 the sixth. Length of body, 1.50 mm.; length of wing, 1.75 mm.; length of cor- 

 nicle, CLIO mm. (Measurements made from specimen mounted in balsam.) 



In 1850 Doctor Fitch described the corn leaf-aphis (Aphis maidis), 

 and up to 1891, when it was described by Doctor Forbes, what is 

 now known as Aphis maidi-radicis was supposed to be only a root 

 form of that found on the leaves. No one. however, has been able 

 to trace a sexual relationship between the two. Although the sexual 

 forms of .1. maidis have never been observed, it does not seem 

 possible that such a relationship as was previously supposed can 

 really exist. Besides, while, as shown by map on page 114. Aphis 

 maidi-radicis is confined to the country east of the one hundredth 

 meridian. Aphis maidis occur- from Maine to southern California. 



THE ERIGERON ROOT-APHIS. 

 i 1/////.V middh toni Thos. I 



The >pccies Aphis middletoni Thos, is* considered here because it 

 has usually been identified a- Aphis maidi-radicis in publications; and 

 because ii i- impossible to study one of these forms on various food 

 plants over a wide extent of country without studying the other. 



So far as is now known Aphis middletoni infests normally plants 

 of the genera Aster and Erigeron, usually in very Large colonies at 

 the crown of the plant just below the surface of the ground or on the 

 Large roots. The only cultivated plants it ha- been known to attack 

 are Cosmos bipinnatus and the China or German asters (Callistephus 

 hortensis), and possibly also dahlias and French artichoke (Cynara 

 scolytmis). 



Aphis middletoni was first described by Cyrus Thomas, in l^7'.». in 

 the Eighth Report of tin- State Entomologist oi Illinois. Since then 

 it has been referred to in literature only in food-plant lists. It ha- 



