40 MASS. EXPERIMENT STATION BULLETIN 168. 



ones. The percentage probably ran considerably below these figures with 

 most bogs, however, especially those with winter flowage. 



It will be observed that late holding of the winter flowage appeared to 

 greatly reduce the Phanerotoma and Pristomeridia parasitism. The writer 

 is inclined to regard this reduction as another rather reliable indication 

 that most of the infestation which appears on a bog, during a season 

 immediately follovv^ng a late holding of the winter flowage, comes from 

 the upland rather than from the bog itself. Fruit worm moths appear to 

 have fairly good powers of flight, and, if they come from considerable 

 distances to a bog which has been cleared of parasites by the late-held 

 winter flowage, they may succeed in eluding their worm parasitism to no 

 little extent. This reduction of the Phanerotoma and Pristomeridia para- 

 sitism appears to explain the fact that the effect of the late holding of 

 the winter flowage in any season, in its reduction of fruit worm infestation, 

 does not endure into the following season as well as might be desired. 



Thirtj'-five fruit worm cocoons which had been kept in the basement of 

 the station screen-house all winter were opened on May 28 and their 

 contents examined, 30 live and 5 dead worms being found, no pupa 

 of either fruit worm or parasite being present. On June 19, 40 more co- 

 coons similarly cared for during the winter were opened and found to 

 contain: 18 parasite cocoons, part of them being Phanerotoma and part 

 Pristomeridia (the adults of both parasites emerging between June 26 

 and July 6); 12 fruit worm pupa?; 1 fruit worm containing a parasite, 

 apparently Phanerotoma about three-fourths grown (the worm being torn 

 open to determine this) ; 1 live unparasitized worm and 8 dead worms. 

 It thus appears that the fruit worm and its two principal worm parasites 

 begin their pupation period at the same time, the change taking place, 

 for the most part, during the first half of June. 



As a rule, only one or two of the black eggs of Pristomeridia are found 

 in a fruit worm parasitized by that species, but in exceptional cases three 

 or even four are deposited. 



Phanerotoma females were induced to parasitize, under observation, 

 eggs of the fruit worm which had been laid in captivitj^ a few hours before. 

 To toughen the eggs so that they might be easily remioved for microscopic 

 examination, the berries on which they were deposited were placed at 

 once in commercial alcohol for several hours. When the eggs thus treated 

 were examined, the Phanerotoma eggs which they contained were easily 

 found. The latter were elongate and rounded at the ends, nearly trans- 

 parent, very delicate and pliable, and without any noticeable markings. 

 They usually appeared curved from end to end, as they lay in the host 

 eggs, but were nearly straight when crushed out of the abdomens of the 

 females. The results of this study show that the idea that this parasite 

 was viviparous, advanced in last year's report (page 109), was erroneous. 



Fruit worm eggs laid the night of July 19 and parasitized under 

 observation by Phanerotoma females the morning of the 20tli were ex- 



