THE CORN ROOT-APHIS AND ATTENDANT ANT. 35 



carried to the nest the same aphis which it had previously brought 

 out. It was a common thing also to see ants transfer young aphides 

 from the roots of sapped and withered plants to those still young and 

 fresh. May 5, 10 aphides were taken from a smartweed root and 

 placed on the bare ground. They crawled actively about, and 2 of 

 them entered a crack in the earth as if to escape the light. One of 

 these was found by an ant, which carried it away. Two small ones 

 crawled about 4 feet and stopped as if exhausted, but 2 larger aphides 

 traveled more than 10 feet in an hour and twenty minutes without 

 finding any food plant. All were seemingly averse to the light, and 

 crawled away from the sun. 



Once a corn root-aphis taken from a plant and placed on the ground 

 was found by an ant and carried away to a distance of 4 feet. It was 

 then left to itself while its attendant ant dug down to the roots of a 

 plant of foxtail grass (Setaria), when the aphis was seized and car- 

 ried into the burrow, where it was afterwards found by digging, 

 contentedly sucking sap from the root. 



Ants often take possession of young aphides as fast as they are 

 born and carry them to new plants, and they are similarly interested 

 whenever oviparous females are producing eggs. Curiously, they 

 pay no especial attention to these females themselves, although the 

 eggs are snatched up and carried away as fast as they appear. They 

 value highly the golden eggs, but take no care of the geese. 



INJURY TO CORN. 



What this pair of associate pests may do to a corn crop is well 

 shown by conditions found this year in a field of corn in Ford County, 

 in central Illinois— a great corn year, in a great corn county, in the 

 midst of the great corn belt. This 20-acre field, in corn for only 

 the second year, and in oats two years ago, had been evidently in- 

 fested the whole season through by the corn root-aphis and by noth- 

 ing else. Immediately beside it was another field, the first year in 

 corn, and virtually free from noticeable insect injury. For an exact 

 exhibit of the consequences of the aphis infestation careful com- 

 parison was made in September of the condition and yield of 2,000 

 hills, taken at random from each of these two fields. In the infested 

 field 23 per cent of the hills were vacant — that is, wholly without 

 plants — and another 21 per cent contained only small dead stalks — 

 44 per cent of the hills either vacant or dead. In the other field 5 

 per cent of the hills were vacant and none were dead. In the in- 

 fested field the plants varied from 6 inches to 6 feet in height and 

 numbered 125 per hundred hills. In the uninfested field the corn 

 ranged from 6 feet to 8 feet in height, with 216 stalks per hundred 

 hills. In the infested field only 4 per cent of the stalks bore ears, 

 and in the uninfested field only 4 per cent of the stalks were barren. 



