INSECT ENEMIES OF EASTERN FORESTS 129 
of much importance economically. Some species may be found wher- 
ever their hosts grow in the United States, though most of them appear 
to be confined to the eastern half of the country as far south as the 
Carolinas. 
A list of these species with their hosts is as follows: Calaphis 
betulella Walsh, various species of birch; Calaphis betulaecolens 
(Fitch), various species of birch ; ; Huceraphis betulae (Koch), various 
species of birch and Japanese maple: Monellia caryella (Fitch) and 
Monellia costalis (Fitch), hickory, walnut, butternut, and oaks; 
Myzocallis alnifoliae (Fitch), various species of alder; M yzocallis 
discolor (Mon.), oak and hickory ; I/yzocallis ulmifolii ( Mon. ), Amer- 
ican, winged, slippery, and English elms; Vherioaphis Dae (Walsh), 
oak; Therioaphis tiliae (1.), native and introduced lindens; Chaito- 
phorus populifoliae Oest., various species of poplar; Neothomasia 
populicola (Thos.), various species of poplar; Periphyllus lyropictus 
(Kess.), Norway and sugar maples; Periphyllus americanus Baker, 
sugar and vine maples; “Periphyllus negundinis (Thos.), boxelder: 
Drepanaphis acerifoliae (Thos.), various species of maple; Drepano- 
siphum platanoides (Schrank), Norway, English, and sycamore 
maples; Phyllaphis fagi (1.), practically all species of beech; 
Clavigerus smithiae (Mon.), various species of poplar and willow; 
Clavigerus populifoliae (Fitch), various species of poplar; and 
Clavigerus salicis (Li.), on various species of willow. 
TrinE APHIDINI 
One species, Anuraphis crataegifoliae Fitch, occurs on hawthorn 
from New England to Illinois, but is of little importance. 
TrRIinE HRIOSOMATINI 
Only three species belonging to this tribe are of sufficient impor- 
tance as pests of forest and shade trees to warrant discussion in this 
manual. They are Lriosoma americanum (Riley) and £’.. rileyi Thos., 
found on American elm; and the woolly apple aphid (£. lanigerum 
(Hausm.)), found on American, wych, smooth-leaved, and slippery 
elms. 
Eriosoma lanigerum is one of our commonest elm aphids. It is also 
a pest of apple, which is important, because this tree is directly involved 
in the biology of the aphid. A discussion of the morphological char- 
acteristics of the species seems unnecessary, since it may be recognized 
easily by the type of injury it causes. It probably is to be found in this 
country wherever apples are grown. 
The life history of H7osoma lanigerum is interesting and complhi- 
cated. The egg-laying female generally deposits her egg in a crevice 
of elm bark. Occasionally she Tays it on another species of tree. In 
the spring the egg hatches and the stem mother migrates to the base of 
a bud. As soon as the leaves appear she begins to feed, and the 
affected leaf curls or forms a rosette about her. In this curled leaf 
she produces her young—the second, or spring generation, which con- 
sists of wingless viviparae that also live in and feed on the curled leaf. 
This generation matures about a month after the stem mother has 
emerged from the egg, and it produces the third generation, which 
is winged and is known as the spring migrant. 
