TACHINID PARASITES OF THE GIPSY MOTH. 227 



1906, this was colonized the most satisfactorily, or so it is believed 

 (having been confused with Tricholyga grandis it is impo*ssible 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 T. 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 T. 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 chelonise. 



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 JAPONIC A TOWNS. 



Pretty nearly all that has been said of Tachina larvarum may be 

 said with equal truth of Tachina iaponica, 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, 



