34 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



A single colony of worker ants may extend its burrows in the 

 cornfield under an area 3 or 4 feet in diameter and to depths usually 

 varying from 1 to 4 or 5 inches, but the deeper chambers are some- 

 times 6 or 7 inches below the surface. During a summer drought the 

 ants may bury themselves a foot or more, piling up in sluggish heaps 

 in the deeper chambers of their nests. 



These ants are thoroughly devoted to the root aphides in their 

 charge, although not wholly dependent on them for food. In ant 

 nests without aphides we have sometimes found the debris of various 

 insect bodies — larva?, beetles, and the like — and in one case a common 

 white grub. We have also seen this ant eating an earthworm. 



Until this year I have never known it to injure directly the corn 

 plants, among whose roots it mines so diligently, but late last May 

 my attention was called to, a field near Champaign, 111., heavily in- 

 fested by these ants, which were present in unusually large colonies, 

 and in nearly all cases with no root aphides in charge. Some 4.000 

 ants in 24 colonies had less than a hundred aphides among them — less 

 than 1 aphis to every 40 ants. Forty to 50 per cent of the hills of 

 this corn were suffering seriously, because the softened kernels had 

 been eaten out by the ants while the plant was still too small to feed 

 sufficiently by the roots. This field was in oats last year, in corn in 

 1903, and a meadow in 1902. 



RELATIONS OF ANT AND APHIS. 



The relations between the aphides and the ants are so intimate and 

 important that the numbers of the aphis are strictly limited by the 

 numbers, activities, and industry of the ants. That the latter are 

 fully equal to their usual opportunities is shown by the fact that 

 through the spring months a large proportion of the burrows which 

 they have excavated in the fields are without aphides, being evidently 

 prepared in advance of the existing supply. It is only toward the 

 middle of the summer that one will find, as a rule, every ant colony 

 with its aphis family in charge. 



The care taken of the aphides by the ants is well illustrated by a 

 number of incidents reported to me by one of my assistants. Mr. E. O. 

 G. Kelly, from among his observations in the field last spring. April 

 12. for example, he watched for two hours and a half an ant nest, 

 near which a few small smartweed plants were growing. An ant 

 coming up with a young aphis in its mandibles, carried this about 2 

 feet and placed it on a smartweed near the ground. Within the next 

 20 minutes, six more ants transferred each a single aphis from their 

 underground burrows to smartweeds above ground. In about an 

 hour and a half one of the ants returned for its aphis and took it to 

 the nest, and 35 minutes later all had been carried back. One of these 

 ants, which was so marked that it could be recognized on its return, 



