SUMMER MEETING. 23 



rophytic fungi and bacteria enter the dead and decaying portions and 

 help to hasten the work, and soon that portion of the root perishes. 

 Sometimes the root seems to be killed outright by the vast number of 

 aphis sucking the sap and causing the abnormal growth, so that the 

 attacked portion perishes before decomposition has fairly set in. But 

 in either case the aphids perish or leave the dead root and seek living 

 roots upon which they can feed, and hence, when one examines a root 

 that has been dead for only a short time even, the aphis may not be 

 found there, and this has lead many to attribute the death of the root 

 to other causes, especially to " root-rot." As the wooly-aphis attacks 

 in immense numbers the main roots at or near the trunk, and as these 

 roots are usually eventually killed and then rapidly decay, the tree 

 loses its support and falls with the first wind. 



It is remarkable how long an apple tree will manage to live after 

 its main roots have been killed by the wooly-aphis. It puts forth 

 numerous small rootlets that nourish the tree enough to keep it alive 

 with about half the usual number of leaves, but these rootlets are not 

 sufficient to hold the tree upright. 



No variety of apple tree in Missouri appears to be exempt from 

 the attack of the wooly aphis, nor does the age of the tree appear to 

 make any difference. It attacks and injures alike seedlings, nursery 

 stock, young and old bearing trees, but very old trees appear to with- 

 stand this test much better than young ones. 



This insect is well known to all fruit-growers in Missouri, and it 

 needs no scientific description. A very brief statement of its life 

 history may, however, be useful. The adult insects are found in two 

 forms, as can be seen by carefully examining a colony late in the sum- 

 mer. One form has wings and does not excrete the downy matter, 

 while the other and more numerous form has no wings and excretes 

 from the pores of its abdomen the bluish-white downy of cottony mat- 

 ter that covers the insect and renders it so conspicuous. If this downy 

 substance be touched, it will be easily removed from the insect, which 

 will immediately excrete more. 



The solitary eggs of tnis wooly-aphis may be found during the 

 winter in the crevices of the bark at or near the base of the tree, where 

 they are usually seen completely enveloped in the dead skin of the 

 mother who lays the single egg. In the spring these eggs hatch into 

 wingless, agamic females. These females then bring forth living young 

 rapidly and without males — parthenogenetically. These young are 

 also always wingless, agamic females. Their offspring do likewise. 

 This is continued during the summer, each generation being apterous 

 agamic females only. Toward the latter part of summer winged, agamic 



