REPORT OF CRANBERRY SUBSTATION FOR 1915. 41 



amined microscopically the morning of the 24th, five larvce of the parasite 

 being found to have hatched. The incubation period of this parasite is 

 certainly, therefore, not longer than four days, and may be considerably 

 shorter than that. 



Seven eggs laid bj' fruit worm moths in captivity some time between 

 8 P.M. July 18 and 8 a.m. July 19, 1915, were parasitized under observation 

 by Phanerotoma females between 9 a.m. and 12 m. July 19, and all of them 

 hatched between 4 p.m. July 26 and 8 a.m. July 28, four doing so before 

 8 A.M. July 27. 



The idea, advanced in the last annual report (page 112), of increasing 

 the natural effectiveness of the Braconid (Phanerotoma) parasites by 

 harboring them artificially during the winter is found to be impracticable 

 principally because of the interference of the Chalcidid {Trichogramma) 

 parasite, as the latter develops as readily in fruit worm eggs in which 

 Phanerotoma eggs have been deposited as in those which have not been 

 attacked by that parasite, and when both parasites attack the same egg 

 the Braconid is destroyed by the very rapidly developing Chalcidid. As 

 the Chalcidid is considerably the more abundant parasite of the two, this 

 interference is sufficient to very largely nullify whatever advantage might 

 be gained with considerable effort in the way suggested. 



As is shown by Table 19, the examination of fruit worm eggs from a 

 number of bogs that were reflowed in June and from adjoining ones that 

 were not reflowed seemed to indicate that the flowing in some way not 

 apparent had the effect of increasing the Trichogramma parasitism very 

 markedly. This, however, did not appear to result in the corresponding 

 decrease in fruit worm injury that might reasonably have been expected. 

 Possibly the destruction of predacious forms (ants, spiders, etc.) caused 

 by the reflow largely offset the advantage that otherwise would have been 

 obtained from the increase in parasitism. 



