46 ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
oratory experimenters, working with 
species having both winged and wingless 
agamic females, have succeeded in caus- 
ing the aphids to produce winged forms 
or only wingless forms at will by sub- 
jecting the insects to certain tempera- 
tures and by introducing certain chemi- 
cals into the food-plants. 
Plant-lice increase very rapidly, some 
species producing 20 or more generations 
in a single year, each female on arriving 
at maturity producing in course of time 
from 10 to 400 eggs or young, as the case 
may be, and varying with the species. 
Their numbers are kept in check by a 
large number of natural enemies. These 
include parasitic wasps of the families 
Braconidae and Chaicididae. and preda- 
eceous forms such as lady-bird beetles 
(Coccinellidae), Syrphus-fly maggots (Syr- 
phidae), spiders, larvae of lace-wing flies 
(Chrysonidae) and aphis-lions (Hemer- 
obidae), and certain predaceous Heterop- 
tera. Ants attend aphids to feed on the 
sweet substance excreted by them, and 
in certain forms play the role of hus- 
bandmen towards them, carrying them 
off and caring for them during the win- 
ter months. 
Bibliography 
A complete bibliography of economic 
plant-lice would occupy too much space 
for the purpose of this paper. The fol- 
lowing references include literature deal- 
ing with practically all injurious species: 
“Insect Pests of Farm, Garden and Or- 
.chard”; E. D. Sanderson (John Wiley & 
Sons); 1912. 
“The Aphides Affecting the Apple’; 
A. L. Quaintance (U. 8. Dept. Agric. Cire. 
No. 81); 1907. 
“The Melon Aphis”: F. H. Chittenden 
(U. S. Dept. Agric. Cire. No. 80); 1906. 
“The Woolly Aphis of the Apple’: C. L. 
Marlatt (U. 8. Dept. Agric. Cire. No. 20); 
1908. 
“The Pea Aphis”; F. H. Chittenden (U, 
S. Dept. Agric. Circ. No. 43); 1909. 
“Two Plant-Lice of the Peach’: C. P. 
Gillette and G. P. Weldon (Colo. Agric. 
Exp. Station, Bull. 169); 1910. 
“A Few Orchard Plant Lice’: C. P. 
Gillette and HE. P. Taylor (Colo. Agric. 
Exp. Station, Bull. 133); 1908. 
“The Potato Plant Louse’; EH. M. Patch 
(Maine Agric. Exp. Station, Bull. No. 
147); 1907. 
“The Corn-Leaf Aphis and Corn-Root 
Aphis”; F. M. Webster (U. 8S. Dept. Agric. 
Cire. No. 86); 1907. 
“The Spring-Grain Aphis’; E. M. Web- 
ster (U. S. Dept. Agric. Cire. No. 85); 
1907. 
APPLE 
The Green Apple Aphis 
Aphis pomi De Geer 
This is the green aphis that is often 
very abundant on the leaves, young 
shoots and young fruit of apple and pear. 
It also infests quince, pomegranate and 
occasionally plum and hawthorn. Its life 
history is as follows: A week or so be- 
fore the buds open in the spring the 
young dark green stem-mothers com- 
mence hatching from the winter eggs and 
for a time feed on tender bark or on the 
bud seales. After the buds open they 
confine their attentions to the foliage. 
In about 25 days the lice are full grown, 
pale green with a dark head, cornicles 
and tail. The stem-mother lice are always 
wingless. Upon attaining maturity they 
at once begin depositing young, produc- 
ing within three weeks from 25 to 100 
young. A few of the lice of the second 
Fig. 1. Wingless Female of Green Apple Aphis. 
Stem Mother—Greatly enlarged. PP P 
—Author’s Illustration. 
