April, ’18] 
BECKER: WOOLLY APHIS 
255 
Baker, 1 in suggesting that Eriosoma cratcegi is a synonym of Erio - 
soma lanigera, pointed out that the principal difference between the 
species was in segments Y and VI which were proportionately longer in 
the former species. As previously indicated, our data show that these 
two segments are proportionately longer in our Crataegus reared 
aphids. 
Through the courtesy of Mr. Baker the writer was permitted to ex¬ 
amine a mount of cratcegi migrants. A photograph was taken of a 
typical antenna of this species and photographs of lanigera migrants 
were made in comparison. All are taken at the same magnification 
(about 48 X), and are represented in the accompanying plate. It will 
be noticed that Nos. 5 and 8, antennae from Crataegus reared aphids, 
are strikingly similar to the antenna of cratcegi, figured in 9. 
If measurements and structural differences are to be used as a 
basis for dividing them, it would hardly be possible for us to regard 
cratcegi and lanigera as two species. 
Conclusions 
(1) The life-history of Eriosoma lanigera in the Ozarks is the same as 
recorded for Maine and for Vienna, Va., with the exception that there 
are probably more than two generations of apterous vivipariae on apple 
and Crataegus. 
(2) Experiments with apple root forms indicate that there may be 
from six to twelve generations a year in the Ozarks. 
(3) Elms have acquired a strong degree of immunity against this 
species. Susceptibility to attack seems to be correlated with back¬ 
wardness of growth in the spring. 
(4) Crataegus crus galli is largely immune to the insect, the condi¬ 
tion of immunity being apparently inherent in some instances and con¬ 
ditional in others. 
(5) Northern Spy stock is immune to the species. 
(6) Apterous vivipariae from Crataegus will establish on apple and 
apterous vivipariae from apple will establish on Crataegus though the 
Crataegus individuals do not establish as readily on apple as do the 
individuals from the same host. 
(7) Based on a study of the antennae, the writer’s data indicate 
that Eriosoma cratcegi Oestlund is a synonym of Eriosoma lanigera 
Hausmann. 
Report No. 101, U. S. Department of Agriculture, Office of the Secretary, 1915. 
