INSECTS INJURIOUS TO CORN. 255 



before the corn is put in the ground and place the aphids on the roots. 

 Tliese aphids cannot reach the roots of the smart-weed plant by dieir own 

 exertions, but must be placed there by the ants. They then extract the 

 sap from the smart-weed and soon become grown, bringing forth living 

 young, thus establishing a colony at this place. 



I might add here that the reason that these ants take care of the aphid 

 eggs and of the aphids in the way they do is because of the fact that these 

 aphids excrete a sweet liquid which the ants feed upon and prefer to any 

 other food. Figure 11 shows one of these aphids greatly enlarged. You 

 will notice two short tubes projecting from near the end of the abdomen. 

 These are known as honey tubes. They are represented- more enlarged 

 at a. 



While these aphids that hatch from the winter eggs are continually 

 bringing forth living young, in about two weeks their offspring are able 

 to bring forth living young also, these offspring being wingless, agamic 

 females also. Thus in a very short time we have a very large colony of 

 these aphids established upon the roots of the young smart weed. After 

 a time we have produced from these wingless, agamic aphids, by bringing 

 forth living young, some aphids that have wings. One of these young 



aphids just developing its wings is shown in fig- 



ure 14, enlarged twenty-one diameters, and a full 

 grown one with its fully developed wings is shown 

 enlarged sixteen diameters in figure 15. 



These winged aphids leave the colony and fly 

 through the air without any apparent thought on ■ / ^ V 



their part as regards direction. They are very Jli/[ V-^,|\ 



apt to be carried by the wind, sometimes for con- \ I %^- ■ - \ ■ V, 



siderable distances. They may alight in a corn ('\r 'f,! S 

 field or in a grass field, as the case may be, the I ^Sip^^ 

 whole matter seeming to depend wholly upon I "^.^.. 



chance. If these aphids alight in a g-rass field, '-"^- ^— 



the little red ants that are always found there take pjg 14 _ corn-Root- 

 them and carry them to their burrows and place ^u?il' eniarfedTvfSy^one 

 them upon the roots of fox-tail or pigeon grass, ^^^"^^^ers. 

 which may be found in these fields. On the roots of these plants the 

 aphids extract the sap and bring forth living agamic females, thus estab- 

 lishing a colony. If, however, the winged, migrating aphids happen to 

 alight in a corn field, which corn field may be the first year following grass 

 or other crop, these ants, which are always found there, will also carry 

 the aphids to their burrows, which are down about the roots of the corn 

 plant, and place them there, where they also bring forth living young, 

 which are without wings, and thus establish a colony. 



