8 FAEMEES' BULLETIN 891. 



months and shorter during the summer months. Since each female 

 gives birth to 40 or 50 young, and the young mature and themselves 

 give iDirth to young in from 6 to 8 days during the summer months, 

 it may be easily understood that they increase to enormous numbers 

 and that the killing of one aphis early in the season is equal to the 

 destruction of hundreds or even thousands in midsummer or later. 



The first two or three generations live entirely on the roots of 

 weeds, but as soon as the newly planted corn sprouts the ants transfer 

 the aphids to the more succulent cornroots. Aphids are to be found 

 on both corn and weed roots throughout the summer, wingless indi- 

 viduals always predominating ; but after the second or third genera- 

 tion a considerable number of the aphids may be winged, and many 

 of these make their exit from the ground through the ant tunnels 

 and fly away to a new field. If they chance to alight near an ant 

 hill, they are seized immediately by the watchful ants, carried into 

 the burrow, and placed on a convenient root, giving rise to another 

 infestation. Thus it happens occasionally that corn on new ground;, 

 but near heavily infested fields, becomes so badly infested in late 

 summer, especially if the season is unfavorable to corn, that the crop 

 is damaged noticeabl}^ — a consideration which makes community 

 cooperation an important measure in fighting this as well as many 

 other field-crop pests. 



The males and the egg-laying females begin to appear about the 

 first of October, and the eggs laid by these females are immediately 

 stored by the attendant ants. As cold weather approaches the ants 

 carry the eggs with their own young deeper into the soil, and usually 

 by the middle of November, in the latitude of Illinois and "Wisconsin, 

 all will be found 8 inches or more below the surface, which is below 

 the ordinary plow furrow — and this should be kept in mind when 

 plowing is done in the fall in order that the ant colonies may be 

 destroyed. Similarly in summer, during periods of drought, the 

 ant colonies may be found 8, 10, or even 12 inches below the surface. 



RELATION BETWEEN ANTS AND THE APHIDS. 



As has been stated, the relation between ants and the corn root- 

 aphis is intimate. Several species of ants are concerned, but by far 

 the most common species occurring in fields is the small brown ant 

 frequently spoken of as the " cornfield ant," ^ In the fall the ants 

 carry the aphid eggs to their nests and care for them as they do for 

 their own young, and in spring when the eggs hatch they tunnel 

 along weed roots and place the helpless aphids on the host plant. 

 (Fig. 5.) The aphids are cared for in the same way during the 



^Lasius nlger L., var. americanus Emery. 



