CONTRIBUTIONS ON THE CORN ROOT- APHIS. 101 



ing corn; they reproduced and the colony was kept on corn till November 30. 

 Many oviparous females and 2 winged males were produced by this colony. 

 The sexual forms appeared October 15. Experiment b: Apterous vivipara were 

 removed from the roots of Ambrosia and placed on sprouting cotton, September 

 24. The colony continued till November 16, producing oviparous females 

 October 28. 



Chenopodium album (lamb's-quarters). — Two vivipara and 1 oviparous 

 female were removed from this plant to sprouting cotton. This colony did well 

 till November 11, when the 2 oviparous females it contained were removed to 

 alcohol. 



Diodia teres (buttonweed). — Experiment a: Female specimens were removed 

 from the roots of this plant to cotton, July 29 ; the colony did well till August 

 10, when it was killed by the death of the cotton plant from disease. Experi- 

 ment 6: Wingless females were removed to corn, July 28. Young were pro- 

 duced and the experiment was continued till August 30. Experiment c: Seven 

 wingless females, which had produced young on corn in experiment 6, were 

 removed to cotton, August 14. They produced young on the cotton and the 

 colony was continued till November 22, when it was discontinued. No sexual 

 forms were produced. 



Diodia virginiana (buttonweed). — Female individuals were removed from 

 the roots of this plant to sprouting cotton, September 25. The colony did well 

 till December 4, when it was discontinued. No sexual forms were produced. 



Leptochloa flliformis. — Experiment a: Females were removed from the roots 

 of this plant to sprouting cotton, September 13. The colony was continued till 

 December 8 without producing sexual forms. Experiment 6: Females were re- 

 moved from the roots of Leptochloa to corn. This colony continued till De- 

 cember 4. Oviparous females and a winged male were produced, and eggs 

 were laid. 



Corn. — Wingless females were removed from the roots of corn in the field to 

 sprouting corn in a vial, June 16, and on July 15 females were removed from the 

 corn in this vial to sprouting cotton, where they established a colony which 

 was continued till August 16. 



These experiments show that if the apterous females of Aphis 

 maidi-radicis are transferred to the roots of corn or cotton from sev- 

 eral of their wild food plants or if they are transferred from corn to 

 cotton they will produce young and establish colonies. Thus it is 

 possible for the ants to transfer the aphides from a dying food plant 

 to any other one of a large range of food plants. Fortunately there 

 are many cultivated plants, such as clover, cowpeas, wheat, oats, and 

 rye, used in various systems of rotation, which this insect feeds on not 

 at all, or only rarely and for a short time. 



Mr. G. G. Ainslie experimented in a different manner near Marion, 

 S. C, to determine the same points. Seeds of a number of species of 

 cultivated plants were planted near infested corn rows, trusting to 

 ants to transfer the aphides from one plant to another. These intro- 

 duced plants were examined June 5, with the following results: 

 Muskmelon plants near infested cotton were well provided with 

 aphides, several of the wingless ones being found with young about 

 them. Turnip plants near infested cotton had few aphides on 

 40842— Bull. 85, pt 6—10 2 



