Apr. 1, 1925 
Two Imported Egg Parasites of the Gipsy Moth 
671 
1,100 feet. For the fourth and fifth 
years the averages were 2,520 and 
4,650 feet, and the extreme spreads 
3,600 and 4,800 feet, respectively. 
There seemed to be very little evi¬ 
dence in these collections to indicate 
that Anastatus spread more rapidly in 
one direction than in another. The 
spread to the north and northwest was 
greatest in some colonies, but other 
colonies showed the greatest dispersion 
in the opposite direction. The wind 
probably is an important factor in the 
dispersion of this parasite, for the 
female is not known to fly, although it 
has great jumping ability, and if a 
gentle wind stirs it into activity, caus¬ 
ing it to jump often, it would without 
doubt be carried considerable distances. 
The nature of some of the recoveries 
indicates strongly that the females are 
blown distances of 300 and 400 yards, 
for several collections of gipsy moth 
eggs made along the same line a hun¬ 
dred yards apart often show no pres¬ 
ence of Anastatus, although the species 
will be found present in the eggs col¬ 
lected farther from the center. 
PERCENTAGE OF GIPSY-MOTH EGGS 
PARASITIZED BY ANASTATUS 
In order to ascertain the amount of 
parasitism of the gipsy-moth eggs by 
the introduced parasites, collections of 
the host eggs have been made each year 
from many points over the infested 
area. The percentage of parasitism by 
Anastatus which has been found in a 
majority of the collections is very 
encouraging. 
The gipsy-moth eggs collected from 
the colony sites usually show the pres¬ 
ence of Anastatus the year after colo¬ 
nization. In such cases the amount of 
parasitism is small, but it increases year 
after year until the maximum is 
reached. Because Anastatus spreads 
only short distances some gipsy-moth 
eggs which are collected in the newly 
colonized territory, but not from 
colony sites, often show no parasitism. 
Very many collections of host eggs 
have been made to determine the per¬ 
centage of parasitism. This work has 
been carried on most intensively in the 
areas which have been colonized 
longest, and for the most part at Pea¬ 
body, Mass., and neighboring towns. 
Each sample collection of eggs con¬ 
tained, when possible, 10 egg clusters. 
A collection was made at the center and 
along eight lines, from the center to the 
four cardinal and the four intermediate 
points. The collections within 600 feet 
of the center were made at intervals of 
100 feet, and at greater distances at 
intervals of 100 yards. 
The collection of gipsy-moth eggs 
was carried on intensively at Peabody 
from 1910 until .the spring of 1921. 
The parasitized eggs obtained were 
used for new Anastatus colonies. The 
information obtained by the examina¬ 
tion of these sample collections was 
found useful in determining the area 
over which it would be practical to do 
general collecting to obtain Anastatus 
for colonization. 
A summary of the percentage of 
parasitism obtained from the Peabody 
collections is presented in much abbre¬ 
viated form in Table III. Figure 8 
shows the points where the egg col¬ 
lections were made. 
At Peabody the first colony of 
Anastatus was liberated in 1909. In 
1910 another colony was liberated, and 
a third in 1911. The 1910 colony was 
liberated about 1 mile southeast, and 
the 1911 colony about one-fourth mile 
nearly east, of the 1909 colony. 
Table III.— Parasitism of eggs of the gipsy moth collected at and near Peabody 
Mass., for the specified years and distances from center of colony 
Year eggs collected 
At 
center 
From 
center to 
600 feet 
From 
200 yards 
to 1,400 
yards 
From 
1,400 
yards to 
2,300 
yards 
From 
2,300 
yards to 
3,600 
yards 
From 
3,600 
yards to 
4,500 
yards 
From 
4,500 
yards to 
5,000 
yards 
Per cent 
Per cent 
Per cent 
Per cent 
Per cent 
Per cent 
Per cent 
1910-11___ 
18 
1911-12__ 
33 
19 
1 
1912-13___ 
17 
17 
1913-14__ 
31 
28 
8 
1914-15__ 
20 
21 
9 
1915-16__ 
29 
27 
17 
6 
3 
1 
1 
1916-17__ 
32 
26 
19 
12 
7 
1 
3 
1917-18__ 
26 
22 
24 
18 
16 
17 
18 
1918-19__ 
4 
19 
20 
18 
21 
15 
17 
1919-20...... 
19 
20 
17 
16 
14 
13 
16 
1920-21__ 
29 
27 
18 
22 
17 
17 
18 
