EXPERIMENTAL WORK WITH CRANBERRIES. 55 



than are the spiders, and, moreover, the parasites affecting the fireworm 

 are probably more or less peculiar to it, while its spider enemies are pre- 

 sumably not so to any considerable extent. 



The Fruit Worm {Mineola vaccinii (Riley)). 



The chief work of the year with tliis insect has been a study of its natural 

 enemies. Nearly a dozen species of its parasites have now been reared, 

 and the complete life-history of the most important one was worked out 

 in a general wa_y. The connection of this parasitic insect with the fruit 

 wonn has not been heretofore suspected. Mr. H. L. Viereck, an expert 

 on the group of insects to which it belongs, has determined it to be a 

 Braconid, to which has been given the name Phanerotoma tibialis (Halde- 

 man). This insect is seen on the cranberry bogs in large numbers every 

 summer during and after the blooming period, but its presence has not 

 been accounted for until now. This year it was seen in greatest numbers 

 during the first tliree weeks of July. The adults had almost entirely 

 disappeared from the bogs by July 26, it being possible to find only now 

 and then one on that date. 



A large number of wormy berries were collected during August, 1912, 

 and kept in cans until Aug. 1, 1913. A careful record was made both of 

 the moths and of the parasites which emerged from them. The wormy 

 berries used in this investigation came from three general locations, as 

 follows : — 



1. The center of a flowed bog (station bog). 



2. The edge of a flowed bog (station bog). 



• 3. A dry bog (that is, one not flowed at any time). 



The record of moth and parasite emergence was kept with these loca- 

 tions in mind. The most interesting points brought out by the record 

 thus obtained were : — 



1. That Phanerotoma tibialis far outnumbered all the other parasites taken 

 together. All the parasites obtained from the berries collected at the center of 

 the station bog, and all but one of those from the berries from the edge of this bog, 

 were of this species. About four-fifths of the parasites from the berries collected 

 from the dry bog were also of this species, but the percentage of other species of 

 parasites was much greater among the forms obtained from the dry-bog berries 

 than among those from the berries of the flowed bog. 



2. The berries from the dry bog produced nearly three times as many parasites 

 in proportion to the fruit-worm moths which emerged, as did the berries from any 

 portion of the flowed bog. 



3. The time of the greatest emergence of the parasites, from the berries from all 

 three locations mentioned, was from June 30 to July 9, inclusive. 



4. As slightly more parasites than moths emerged from the worms of the berries 

 from the dry bog, it seems highly probable that more than 50 per cent, of the fruit 

 worms on that bog last year were killed by these parasites. This shows something 

 of the importance of the natural enemies of this insect which we have been in the 

 habit of considering as being comparatively free from parasites. 



