CONTRIBUTIONS ON THE CORN ROOT-APHIS. 105 



October, and eggs are laid in October and November. The eggs do 

 not hatch until the following spring. Its seasonal history in other 

 parts of the country does not appear to vary materially from that in 

 Illinois. 



RELATION OF ANTS TO THE ROOT-APHIS. 



The life of the corn root -aphis in the cornfields is so dependent 

 upon that of the cornfield ant (Lasius niger L., var. americanus 

 Emery), and vice versa, particularly in the Middle West, that they 

 must be considered together. If it were not for this ant the great 

 damage that is done to corn in this country by the root-aphis would 

 be impossible. The ant is distributed everywhere over North Amer- 

 ica except in the extreme southern and southwestern portions. It is 

 found in cultivated fields, in pastures, in forests, and along roads. 

 A very complete account of the life history of this ant is given by 

 Doctor Forbes in the Twenty-fifth Report of the State Entomologist 

 of Illinois. 



The ants collect the eggs of the aphis in the fall and carry them 

 to their nests, where they are kept during the winter. By bringing 

 these eggs near the surface or carrying them deeper down into their 

 burrows the ants are able to control the hatching of these eggs until 

 weeds spring up upon which the young aphides can feed. As soon 

 as the eggs hatch the young larva? are transferred to the roots of 

 young weeds such as pigeon grass, smartweed, and ragweed. When 

 the corn begins to come up the colonies of the root-aphis are trans- 

 ferred to the roots of corn. The root-aphis, like all other species in 

 this family, secretes and voids a sweet liquid called honeydew, upon 

 which the ants feed. As this honeydew constitutes the principal 

 food of the ants, the strength of each individual ant colony is de- 

 pendent upon the number of aphides in its charge. 



Although Lasius niger americanus is the most important ant that 

 attends Aphis maidi-radicis throughout the territory known to be 

 infested by the root-aphis, it is not the only one thus involved. Two 

 other species that are important in this connection are Lasius flavus 

 Fab., which has often been observed attending the root-aphis in 

 Maryland, and Pheidole vinelandica Forel, which was observed by 

 Mr. J. A. Hyslop attending it at Nathalie, Va., and by Mr. G. G. 

 Ainslie, at Marion, S. C. Among the ants which sometimes attend 

 this species are Lasius (Acanthomyops) murphy i Forel found asso- 

 ciated with this species at Arlington, Va., by Mr. Paul Hayhurst, 

 and the following species, which are reported by Doctor Forbes a as 

 occasionally attending the root-aphis in Illinois : Formica schaufussi 



° Eighteenth Report of the State Entomologist of Illinois. Trans. Dept. Agr. 

 111. for 1893, Springfield, vol. 31, p. 66, 1894. 



