Puant Lice INJuRING FOLIAGE AND FRUIT OF THE APPLE 737 
those of the second. The lice congregate in immense numbers on the 
underside of the foliage, causing severe curling; they also attack the 
setting and developing fruit, producing their characteristic injuries which 
are described later. At Ithaca in 1915, the majority of this generation 
acquired wings and migrated to their summer host plants. 
When the last skin is shed the winged adults are very tender and inactive. 
They remain secreted in the curled leaves for several days, generally two 
or three, before venturing on their migratory flight. They then become 
very active and nervous, running about or moving their wings up and down 
in anticipation of their flight. What factors influence the production of 
winged or wingless forms in this generation can only be conjectured. 
In cage experiments where in some cases crowding became excessive, 
practically all of this generation acquired wings; whereas under similar 
conditions in other cages many of the insects did not acquire wings and 
produced a fourth generation on the apple. Many theories have been 
advanced, based entirely on observation, as to the influence which climatic 
factors, such as heat, cold, or moisture, may have; excessive crowding also 
has been used very generally in explaining the early production of winged 
forms. Unfortunately, thru lack of equipment no experiments could be 
undertaken by the writer to determine the influence of any of the factors 
involved. The importance and significance of the development of the 
winged migrants in any particular generation are very great, not only 
to the biologist, but also, and more particularly, to the orchardist. This 
is pointed out in more detail in the discussion of the summer migration 
of this species. | 
Description of stages 
The early instars of the third generation are practically identical with 
those of the second generation, both in size and in color markings. It 
will therefore be sufficient to describe only the last two instars of this 
generation, restricting the description to the winged forms; the wingless 
forms are practically identical with those of the preceding generation 
and require no special description. 
Fourth instar, winged female.— Length 1.8-2 mm.; width 0.9-1 mm.; 
cornicles 0.26—0.28 mm. long. 
The general color after the molt isa bright pink, which gradually changes 
to a rusty reddish over the entire abdomen, the wing pads shading to 
