12 
many specimens are sent to the Division of Entomology almost every 
week of the two last-named species nnder the supposition that tbey 
are or may be A. perniciosus. As a matter of fact, with a little experi- 
ence, A. perniciosus can be distinguished from either of the other 
species by the scale alone with a hand lens. A. ancylus and A. forbesi, 
however, can not readily be distinguished from each other without a 
microscopic examination of the anal plate of the adult female, although 
the old female scales of ancylus are rather larger and flatter than those 
of forbesi and the exuvia are less conspicuous. Moreover, in winter the 
only mature or nearly mature specimens of forbesi to be found are dead, 
while nearly mature sx^ecimens of ancylus normally overwinter. Pro- 
fessor Johnson has called the writer's attention to this important point. 
There is given below a little analytical key which it is hoped will be of 
service in separating these three species. It is based upon characters 
used by Mr. Pergande, the assistant in charge of the insectary, in his 
daily work of determining these forms: 
Young female scales. 
Dark gray, or, if rubbed, black; toward center more or less distinctly black with 
a more or less distinct central white dot and surrounding ring perniciosus. 
Purplisb or pale grayisb, the margin of the darker scales grayish ; exuvia orange, 
covered with a delicate pale grayish exudation with a- whitish central dot and 
surrounding ring ancylus and forbesi. 
Male scales. 
Yellowish gray or greenish gray; excretion covering the exuvia either concolorous 
or dark gray and with a more or less distinct white dot 2 )er, ^ c ' os " s - 
Purplish, with the margin grayish; exuvia orange and covered with a delicate layer 
of pale grayish excretion and a whitish central dot ancylus and forbesi. 
Old female scales. 
Scale yellowish gray, exuvia yellow. Anal plate, with four terminal lobes; groups 
of pores absent perniciosus. 
Scale pale yellowish gray, exuvia orange. 
Anal plate, with two terminal lobes and live groups of pores, the anterior group 
consisting usually of three, the anterior lateral groups of about twelve, and 
the posterior groups of about eight pores ancylus. 
Anal plate, with four terminal lobes and four groups of pores, each group com- 
posed of from four to six pores (rarely there is a lifth group of one or two 
pores) forbesi. 
FOOD PLANTS. 
It was said in Bulletin No. 3 that practically all deciduous fruit 
trees and various small fruits as well as many shade trees and orna- 
mental shrubs are affected by this insect. A list of food plants was 
given, comprising, in general terms, twenty-eight species. Since then 
about seventeen have been added to the list. A revised list follows. 
