Apr. 1, 1925 
Two Imported Egg Parasites of the Gipsy Moth 
649 
The largest number of Schedius 
which has been recorded at the labora¬ 
tory as developing from a single ferti¬ 
lized female is 191. In these experi¬ 
ments 40 pairs of fertilized Schedius 
were used. The records of four pairs 
were 183, 180, 161, and 152. The prog¬ 
eny of several of the other pairs num¬ 
bered less than 100, and the average 
progeny from one pair of Schedius, 105. 
It is probable that under favorable con¬ 
ditions in the field many Schedius de¬ 
posit at least 200 eggs. 
Records obtained at the laboratory 
show that female Schedius are more 
abundantly produced from fertilized 
parents than are males. One typical 
set of data, concerning over 4,000 
adults reared and examined, shows 
that 74 per cent of the issuing genera¬ 
tion were females. 
In jars at the laboratory there has 
been considerable in-and-in breeding. 
Parents and offspring and brothers and 
sisters have mated, and the first gen¬ 
eration has showed no apparent weak¬ 
ness. In the large reproduction trays 
(fig. 3, a, b ), in which Schedius are 
bred for colonization, there is consid¬ 
erable in-and-in breeding. After five 
or six generations have been produced 
the resulting Schedius are smaller and 
weaker than those of the first few 
generations, probably because of the 
continued in-and-in breeding. 
PARTHENOGENESIS 
Schedius reproduces parthenoge- 
netically, the resulting offspring always 
being males. In laboratory experi¬ 
ments in which females have not been 
allowed to become fertilized the aver¬ 
age number of the progeny has been 
about 50. This is much lower than 
the average number of progeny ob¬ 
tained in similar experiments conducted 
with fertilized Schedius. 
SUPERPARASITISM 
Gipsy-moth eggs which have been 
exposed to Schedius in laboratory ex¬ 
periments often contain more than one 
parasite egg. In these experiments the 
same female often oviposits more than 
once within the same host eggs, and 
occasionally she pierces a host egg with 
her ovipositor but does not insert an 
egg. Hundreds of thousands of gipsy- 
moth eggs collected in the field are ex¬ 
amined with a binocular microscope 
each year, and only a very few cases 
have been observed where more than 
one Schedius has developed within an 
individual gipsy-moth egg. 
HIBERNATION 
The manner in which this parasite 
passes the winter was for a long time in 
doubt. Schedius is present late in the 
fall in gipsy-moth eggs and will often 
issue from eggs collected in December. 
Schedius rarely issue from egg clusters 
collected after winter begins and tem¬ 
peratures of 15° F. and lower are re¬ 
corded. Examination of such eggs 
with a binocular microscope often 
shows all stages of dead Schedius with¬ 
in the eggs. Hundreds of thousands 
of gipsy-moth eggs containing all 
stages of living Schedius have been 
kept through the winter in cold storage 
at temperatures around 30° F. Similar 
lots of eggs have been kept in various 
types of containers, under as nearly 
natural conditions as possible, in cages 
in the laboratory yard. Such experi¬ 
ments have been tried during a number 
of years but in no case has a single 
adult Schedius been obtained the fol¬ 
lowing spring. 
Many experiments similar to those 
just mentioned have been conducted 
with adult Schedius to obtain positive 
records of adult hibernation. Such 
experiments often failed to carry 
Schedius through. In the next suc¬ 
ceeding paragraphs are described the 
first experiments in which the proof 
was positive that Schedius were carried 
successfully through the winter as 
hibernating adults. 
A wooden tray (10 by 10 by 4 inches) 
with a wooden base was prepared for 
the hibernating experiment. On the 
inner sides were tacked several small 
strips of felt and pieces of cotton bat¬ 
ting. Several small pieces of such pad¬ 
ding were folded and moistened with a 
solution of one-half water and one-half 
honey. This tray after being stocked 
with Schedius was placed in a Riley 
cage in the yard and left there until 
completion of the experiment the fol¬ 
lowing summer, except when it was 
taken into the laboratory for observa¬ 
tion. 
On October 6, 1915, about 50 adult 
Schedius and a few gipsy-moth eggs 
were placed in the tray. The several 
observations which were made up to 
November 10 showed Schedius to be 
active, but many adults had died. On 
this date a few more adults were added. 
On November 18 some Schedius were 
still alive, especially on the sides of the 
cage close to the felt. On December 21 
the temperature at the laboratory yard 
descended to 13° F., but on December 
23 Schedius were still alive. A number 
were clinging to the sides of the tray 
