PARASITES HIBERNATING IN BROWN-TAIL WEBS. 
285 
The diversity in the host relations of the parasite thus indicated is 
also encouraging. If it is capable of attacking arctiid as well as 
notodontid caterpillars with as much apparent freedom as it does 
liparids, there ought always to be plenty of available hosts to cany 
the species over the two or three months which must elapse after its 
emergence from the hibernating brown-tail moth before it can attack 
the young caterpillars of the same species for a second generation. 
1 1 was hoped for a time that it would succeed in passing one generation 
upon the gipsy moth, but although it has been forced to oviposit in 
gipsy-moth caterpillars, and its larva* have upon a single occasion 
attained their full development upon this host, there is no indication 
that it evei- attacks it voluntarily in the field. 
It is interesting and perhaps significant that in it> relations with 
Datana it affects the host caterpillars exactly as in its relations with 
the brown-tail moth. The caterpillars died before the emergence of 
the parasite larva?, and were left as nothing more than mere skins con- 
taining a small quantity of a clear liquid. In this respect, Apanteles 
lm t< [color Vier. differs materially from .1. solitari us, or from many 
other among its congener^, which leave the host in a living condition 
but so seriously affected as to be unable to feed again. 
Just as the proof of this bulletin is being read (June 12, 1911) word 
is received from the laboratory at Melrose Highlands that 4,000 
cocoons of this parasite have been secured from brown-tail moth webs 
taken in the field in Maiden and other towns. 
APANTELES 0ON8PERSJS FISKE. 
In the summer of 1910 several boxes of the cocoons of an Apanteles 
parasitic upon the Japanese brown-tail moth, Fji])r<>v1is conspersx 
Butl., were received at the laboratory through the kindness of Prof. 
S. I. Kuwana. All of them had hatched at the time of receipt, and 
the circumstance would hardly be worthy of mention were it not for 
the fact that the adults which were dead in the boxes proved upon 
examination by Mr. Viereck to be identical in all structural character- 
istics with Apanteles lacteicolorYier. It would appear that here was 
still another example of that phenomenon which has several times 
been mentioned without having been particularly designated, but 
which is, in effect, the existence of what has been termed "physio- 
logical" or "biological" species. 
It is not so difficult to conceive as to find proof of the existence of 
two species which are so nearly alike structurally as to be indistin- 
guishable by any taxonomic characters commonly recognized, but 
which are, at the same time, different. This difference may be 
exemplified by the sex of the parthenogenetically produced offspring, 
as in the instance of the European and American races of Tricho- 
gramma pretiosa. It may lie in the instincts of the female, which lead 
