INTERDEPENDENCE OF ORGANISMS 51 



Hemiptera) so as to completely enclose the flock. With 

 but a few small openings left through the walls for entrance 

 and exit, the guarding of the flock is easier and the security 

 of the flock is greater. The aphids no longer "run the 

 range," but are kept in folds. Excesses of heat and cold 

 are less felt, and the great injury from exposure in rainy 

 weather is largely avoided. The ants probably reap the 

 usual rewards of good husbandry in the larger and more 

 constant secretion of honey dew. 



The sheds are of two sorts as regards the materials of 

 which they are made : i ) earthen sheds, made of sand grains, 

 etc., stuck together with wet clay, and 2) felted sheds made 

 of interwoven bits of shredded plant tissues. Both sorts 

 are often placed about the stems of bushes (fig. 38) and 

 supported on branches or leaf stalks. 



Finally, there is a permanent association, with the ants 

 exercising care and control over the aphids in all stages of 

 their development. This is complete domestication. The 

 best known case of it is that of the little brown ant of the 

 fields and the corn-root aphis. This" subterranean aphid 

 lives on the roots of Indian corn, where these roots traverse 

 the branching passageways of the nests of the ants. It is a 

 hapless creature (fig. 39), quite incapable of uncovering corn 

 roots for itself, or even of finding them if uncovered: so, 

 the ants excavate the soil, making lateral foraging chambers 

 communicating with their nest, and carry the aphids in 

 and place them on the roots. There the aphids feed 

 and secrete honey dew through the season, and in the fall, 

 there they lay their eggs. The following account is quoted 

 from a report on corn insects by Professor Forbes, to 

 whom our knowledge of this relation is chiefly due : 



"These eggs, which are yellow when first deposited, 

 but soon become shining black, and turn green just before 

 hatching, are at first scattered here and there, as it 



