114 



PESTS OF- GARDEN AND FIELD CROPS 



eluding cotton, squash, pumpkin, and strawberries. Plants badly 

 attacked are stunted, lack color, and otherwise show that they are not 

 making a healthy growth. Examination of the roots will then show 

 large numbers of the lice. 



The corn root aphis is cared for, and is dependent on, colonies of ants. 

 The latter are usually the common, small, brown ants of the species 

 Lasius niger americanus Mayr. 



In winter the eggs of the aphis are cared for by these ants, who keep 

 them in their nests, bring them out in the sunlight on warm days and 

 carry them below frost line when the weather is severe. In spring the 



aphis eggs hatch, and the j^oung wingless 

 lice are carried by the ants to suitable 

 weeds, the roots of which will form ac- 

 ceptable food until the corn has sprouted. 

 Thereafter the ants are in constant at- 

 tendance on the lice, transferring them to 

 the roots of corn when the latter become 

 available. 



As warm weather comes on, the lice 

 give birth to a second generation of living 

 young, in which winged individuals ap- 

 pear, and these migrate to new fields. 

 Breeding goes on rapidly, the number 

 of generations sometimes reaching a dozen in the course of the sum- 

 mer. In the fall eggs are laid, and these are cared for again by the 

 ants until another season. 



In control, the most important measure is to plow and harrow in the 

 fall, so as to break up the nests of the ants. Keeping the fields clean of 

 weeds will help materially, depriving the hce of food in the spring. 

 Rotation is of value, since the first generation of the hce are wingless 

 and by the time winged individuals appear corn will be sufficiently 

 advanced to withstand attack from lice that fly in from other places. 

 It is helpful, also, to keep corn growing vigorously. 



Fig. 78. — Larva of Crambus 

 luteolellus Clem. Slightly en- 

 larged. Original. 



