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 carry 

 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. 

 It 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 larvae have upon a single occasion 

 attained their full development upon this host, there is no indication 

 that it ever attacks it voluntarily in the field. 



It is interesting and perhaps significant that in its 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 larvae, and were left as nothing more than mere skins con- 

 taining a small quantity of a clear liquid. In this respect, Apanteles 

 lacteicolor Vier. differs materially from A. solitarius, or from many 

 other among its congeners, winch 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 CONSPERS^ FISKE. 



In the summer of 1910 several boxes of the cocoons of an Apanteles 

 parasitic upon the Japanese brown-tail moth, Euproctis conspersa 

 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 lacteicolor Vier. 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 



