1913.] PUBLIC DOCUMENT — No. 31. 229 



remnant of the bloom was not destroyed. Probably more is 

 lost, as a rule, through injury done to the vines, in harvesting 

 a very light crop, than is gained by saving and marketing the 

 terries. 



Work on fruit-worm parasites was continued, but without 

 any definite results of general value. 



The Flowed Bog Fireivorm {Rhopohota vacciniana (Pack.)). 

 This insect is also known as the blackhead cranberry worm, 

 but it will probably be more readily and generally recognized 

 by the more distinctive name here used. It does little or no 

 damage on bogs that are not winter-flowed. As indicated in 

 the 1911 report, the killing or driving ashore of the natural 

 enemies of this insect by the flowage is probably the main cause 

 of serious infestation by it. In support of the evidence given 

 in that report, the results of this season's collecting of bog in- 

 sects seem rather convincing. Collections were made on sev- 

 eral winter-flowed bogs of great difference in area, at different 

 lengths of time after flooding and at different distances from 

 the uplands, for comparison. Each collection consisted of the 

 material gathered by 100 sweeps of a collector's net through 

 the vines. Three separate collections were made on each day 

 of collecting at each location selected for comparison, to make 

 sure that the collections were truly representative of the insect 

 life present. Comparisons between the different locations were 

 made by separating out the parasitic and predacious forms, 

 classifying them, counting the individuals of each class in each 

 collection separately, and comparing the counts. The most re- 

 markable fact learned from this was that, of all forms capable 

 of damaging the fireworm, spiders were in all cases considerably 

 the most numerous. Moreover, only the spiders gave really 

 striking differences in the counts of the different collections 

 made. The comparisons showed that the dry bog had very many 

 more spiders and also a somewhat larger number of parasitic 

 insects than did any of the winter-flowed bogs, even as late in 

 the season as August 20, when the last collecting was done. A 

 bog of 160 acres of rounded shape gave a distinctly smaller 

 count of spiders, on all parts examined twenty-seven days after 

 the flowage was taken off, than did a bog of 12 acres of similar 



