26 
Toward midsummer man}' of the lice on the twigs crawl down into the 
ground and locate upon the roots. 
APPLE PLANT-LICE. 
The foliage of apple trees, particularly of } T oung trees, often appears 
curled, and sometimes discolored. This curling is produced by colo- 
nies of plant-lice. These lice secrete a sticky liquid known as honey- 
dew, which falls on the leaves below. A black fungus grows upon the 
leaves covered hy the honey-dew, and this checks their growth. There 
are several of these plant-lice that attack the leaves of apple; two of 
them are greenish in color, another has a reddish tinge. 
The commoner of the two green species is known as Aphis mali 
Fitch, (probably Aphis annum Oest). Its life history is about as fol- 
lows: The eggs are laid on the tree in the fall, partly hidden in crev- 
ices of the bark; the young hatch from these eggs in early spring, and 
grow into wingless and sexless lice, known as u stem-mothers, " which 
produce living young; these young become winged, and, in the early 
summer, migrate to grasses, where they increase during the summer. 
In the fall they develop a set of winged, sexless lice, which migrate 
back to the apple and give birth to sexed individuals; these pair, and 
the female la} T s her eggs. 
The other green species is Aphis mali Koch. It passes its entire 
life history upon the apple. The eggs are laid in the late fall. They 
are black, and occur generally on the trunk and branches. In early 
spring the young hatch from these and grow into stem-mothers. These 
produce living young for a number of generations. Many of these of 
the first two generations become winged, fly to other apple trees, and 
there start colonies. In October sexed specimens are produced, and 
the female lays the eggs that are destined to pass the winter. 
The other apple plant-louse is A. sorbi Kalt. It is distinctly tinged 
with red, and the wingless forms have a whitish powdering on the 
body. This species has a life history similar to that of Aphis malt 
Fitch., but it is not known what plants serve as its summer hosts. 
THE TLUM PLANT-LOUSE. 
{Hyalopterus pruni Fabr. ) 
This insect winters in the egg state. The young on hatching in 
spring go to the under surface of the leaf and there multiply rapidly. 
Their bodies are covered by a bluish-white mealy powder. Winged 
specimens are occasionally developed which migrate to other trees. 
They feed on the plum all summer, but some specimens are said to 
migrate to grass in early summer. In the fall the winter egg is 
attached to a plum twig, usually at the base of a bud. At times they 
do considerable damage to young plum stock. 
