TACHINID PARASITES OF THE GIPSY MOTH. 227 
1906, this was colonized the most satisfactorily, or so it is believed 
(having been confused with T’richolyga grandis it is impossible to state 
definitely which of the two was the more abundantly reared and 
liberated that year), and it ought to have been recovered by 1910 if 
it is ever to be recovered as a result of early colonizations. That it 
has not been recovered as a result of the 1909 colonization work is not 
at all surprising, because there is every prospect of two or three years 
elapsing between the liberation and the recovery of any species, and 
more particularly of those which, like Tachina and many others of the 
tachinid parasites of both the gipsy moth and the brown-tail moth, 
are not received from abroad until after the season is so far advanced 
as to make immediate reproduction upon either of the hosts mentioned 
impossible. 
It is unfortunately true that it would be impossible to distinguish 
it from Tachina mella, should it be reared, since 7’. mella is occasionally 
reared as a parasite of the gipsy moth or the brown-tail moth, but it 
is still more unfortunate that no adults of any species which could by 
any possibility be referred to either were reared in 1910 from the 
gipsy moth. 
In 1910 Messrs. Thompson and Tothill conducted an experiment to 
determine whether 7. mella and T. larvarum would hybridize. The 
results were negative, and not of sufficient strength to be at all deci- 
sive. If it could be proved that hybridization took place freely, the 
fact in itself would probably be sufficient to render the European 
species of no account as an enemy of the gipsy moth in America. 
Interbreeding with a vastly superior number of another race, the 
principal and only economically important distinguishing characteris- 
tic of which was inability to breed upon a certain host, would un- 
doubtedly result in the sinking of the racial characteristic, and T. 
larvarum as a race would almost immediately cease to exist. This is 
the more probable in the light of the experiences, yet to be related, 
which attended the attempted introduction of the brown-tail parasite 
Parexorista chelonie. 
On this account, and on no other, Tachina larvarum has been ten- 
tatively eliminated from the list of promising parasites of the brown- 
tail moth and the gipsy moth. It may not establish itself here in 
America, and under the peculiar circumstances, proof to the con- 
trary being lacking, its possible hybridization may make further 
attempts to import it useless. 
TACHINA JAPONICA TOWNS. 
Pretty nearly all that has been said of Tachina larvarum may be 
said with equal truth of Tachina japonica, in so far as its value in 
America is concerned. It may possibly be that it is sufficiently 
distinct as a species to make possible its successful establishment, 
