Apr. 1, 1925 
Two Imported Egg Parasites of the Gipsy Moth 
673 
Table V.— Percentage of 'parasitism by 
Anastatus bifaciatus of gipsy-moth egg 
clusters collected at different heights in 
the trees 
Distance from 
ground eggs were 
collected 
Number 
of egg 
clusters 
Percent¬ 
age para¬ 
sitized 
by Anas¬ 
tatus 
Average 
number 
of eggs in 
each 
cluster 
1 foot to 6 feet. 
40 
40.2 
202 
1 foot to 6 feet.. 
40 
30.7 
273 
1 foot to 6 feet. 
40 
39.7 
165 
1 foot to 5 feet.. 
40 
37.5 
205 
Average.. 
37.0 
211 
35 feet to 40 feet. 
40 
35.5 
280 
20 feet to 35 feet_ 
40 
28.2 
326 
30 feet to 55 feet. 
40 
42.3 
127 
35 feet to 40 feet_ 
40 
37.1 
237 
Average. 
35.8 
242 
Similar collections of gipsy-moth 
eggs have been made in areas where 
Schedius was abundant, to determine 
its parasitism of the eggs on various 
parts of the trees. Only a slight differ¬ 
ence was found in the activity of 
Schedius at different heights, the aver¬ 
age percentage of parasitism at less 
than 6 feet from the ground being 26, 
and that for heights of from 30 to 55 
feet 29. This difference could be ex¬ 
plained by the fact that the higher egg 
clusters averaged only 154 eggs each, 
while those collected at heights below 
6 feet averaged 171 eggs. 
PERCENTAGE OF PARASITISM BY 
ANASTATUS AND SCHEDIUS OF 
GIPSY-MOTH EGGS COLLECTED 
AROUND OBSERVATION POINTS 
During 1911 and 1912 about 250 
points, scattered over a considerable 
part of the area at that time infested 
by the gipsy-moth, were chosen and 
called “ observation points.” A tree 
at the center of each point was marked 
and a circle 100 feet in diameter was 
described around it. Careful records 
of the condition of the growth and in¬ 
tensity of the gipsy-moth infestation 
at each point have been kept for each 
year. 
From 1912 through 1923 collections 
of gipsy-moth eggs have been made 
around many of these points. In 
each case an attempt was made to have 
a typical sample of eggs from which 
to determine the amount of egg para¬ 
sitism. The eggs were collected just 
outside the 100-foot circle in eight 
different directions from the center. 
Two large, two medium, and two small 
egg clusters were collected at each 
of the eight places, a total of 48 egg 
clusters for each observation point. 
Each cluster was separately examined 
at the laboratory. The results are 
presented in Table VI. 
The area covered by the observa¬ 
tion point collections is shown in 
Figure 4. It will be seen that the 
eastern part of Massachusetts and the 
southeastern part of New Hampshire 
are well represented. The egg collec¬ 
tions were not made with reference to 
parasite colonizations and the amount 
of parasitism shown is therefore rep¬ 
resentative for the entire area covered 
by those points. 
A study of Table VI shows that the 
smaller the egg cluster the more heavily 
parasitized it is. The female Anasta¬ 
tus is unable to oviposit in all the eggs 
of a cluster, and the percentage of 
eggs parasitized decreases as the size 
of the cluster increases. When Ana¬ 
status is very abundant and several 
females are present on a gipsy-moth 
egg cluster as it is being laid, the 
parasitism increases, this being espe¬ 
cially true in the case of small clusters. 
It will be noted that during the last 
two years this difference has increased 
materially, the small egg clusters being 
parasitized by over 10 per cent more 
than were the large ones. 
The table shows a steady increase in 
parasitism by Anastatus until the fall 
of 1922, when a slight drop occurred. 
Schedius increased gradually through 
the fall of 1917, but with few exceptions 
has not been able to increase in this 
area since the severe winter of 1917-18. 
PERCENTAGE OF GIPSY-MOTH EGGS 
PARASITIZED BY SCHEDIUS 
It appears from the results shown in 
the foregoing table that Schedius is an 
unimportant factor as an egg parasite 
of the gipsy moth in the area repre¬ 
sented. The climate of this area has 
been too severe during the period 
covered by the collections for this 
parasite to be of general abundance. 
During this period, however, Schedius 
has for several different years been an 
important egg parasite of the gipsy 
moth in numerous locations. The fact 
that it produces several generations 
each year allows it to increase rapidly 
under favorable conditions, and within 
the area under discussion collections 
of gipsy-moth eggs are often made which 
show from 10 to 20 per cent of the eggs 
killed by this parasite. 
Schedius seems better suited to the 
milder climate of southern Massa¬ 
chusetts. For the last five or six years 
it has been increasing in abundance in 
