24 
THE WOOLLY APPLE APHIS. 
(Sckizoncura tanigera Hausmann — figs. 14 and 15.) 
One often notices on the trunk or larger branches of the apple 
Fig. 14.— Schiznneura lanigera; a. agamic female; 5, larva: c, pupa; d, winged female. (Marian.) 
small, bluish-white, nocculent patches of a woolly substance, which 
indicate the presence of this insect. 
This cottony substance is a wax-like 
excretion clinging to the posterior 
parts of a small, reddish -brown 
wingless aphis. It is not, however, 
this form on the trunks that causes 
injury. This aerial form is but the 
indication that there are other speci- 
mens, under the ground and feeding 
on the roots of the tree. It is the 
latter form that seriously affects the 
vitality of the tree. Upon the trunk 
the lice often cause a roughening 
of the bark, especially on the new 
growth around scars made b} T prun- 
ing. On the roots the lice cause 
hard and large knots, which eventu- 
ally produce a " club-footed' 1 con- 
dition of the roots. Such trees 
usually show their weakness by the 
fewer and duller colored leaves. 
The woolly aphis is practically 
confined to the apple, but there are 
a few varieties, such as the Northern 
Spy, that appear to be immune against its attacks. The lice com- 
Fig. 15.—Schizo)icura lanigera; a, b, work on 
roots; c, a louse. (Marlatt.) 
