APHIS HERDS AND ANT ASSOCIATES 



a leaf cause it to shrink up, forming little rolls, or tents, 

 within which immense numbers of the insects dwell. 

 With them ants will commonly be found, attending them 

 simply for their honey-dew; but often they get the blame 

 of the damage done by their companions, an experience 

 that is apt to befall higher creatures. Minute as each 

 individual is, when multiplied by hundreds and thou- 

 sands the injury wrought upon the numerous leaves of 

 the plant is sufficient to affect their health. 



When the punctures are made upon the roots they 

 result in little gall-like swellings, which harden, destroy 

 the natural function of the rootlets, and finally result in 

 death. When a large number of roots is thus affected, 

 the plant, of course, has lost its power of deriving sufficient 

 and wholesome nurture from the earth, and so falls into 

 decay. Other species of aphides secrete from a part 

 or the whole of the body a whitish powder or bloom, or 

 numerous filaments of fine cottony matter in which they 

 become completely enveloped. 



In the various stages of development the nymphs of 

 some species secrete globules of honey-dew several times 

 larger than themselves. Sometimes the globule com- 

 pletely envelops the nymph. After they are moulted, 

 the nymphs usually find a new feeding-place, leaving 

 the old skin attached to the drops of honey-dew. The 

 moulted skins, the last moulted especially, often retain 

 their form so perfectly as to seem like a live nymph. 



Professor Slingerland, in his account of the " pear- 

 tree psylla," 1 says that it ejects immense quantities 

 of honey-dew, which cover twigs, branches, and trunks 

 of the trees, and even the vegetation beneath. This 



1 M. V. Slingerland, Bulletin No. 44, Cornell University Agricul- 

 tural Experiment Station, 1902: "The Pear-Tree Psylla." 



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