REPORT OF CRANBERRY SUBSTATION FOR 1915. 33 



cannot detect any difference between them. The injury to the roots 

 seems to be identical with that caused by R. picipes here, and I therefore 

 offer the opinion that your specimens are Rhabdoptenis picipes Oliv." 



A bog injured by this insect has a general appearance similar to that of 

 one damaged by the cranberry girdler {Crambus hortuellus Hbn.), the 

 patches of dead vines being very irregular in form and distribution. 

 Roots injured by the girdler, however, have the wood as well as the bark 

 eaten considerably, frequently being entirely cut off, while the large and 

 secondary roots worked on by the rootworm show practically no injury 

 to the wood, only the bark being eaten away. The girdler feeds on the 

 surface, concealed in fallen leaves or other trash which lies over the sand, 

 and prefers the runners and crowns of the plants, while the rootworm 

 works in the soil and feeds very largely on the fibrous roots which, though 

 they form a dense mat an inch or more in thickness, are frequently almost 

 completely devoured. 



The bog area which has this newly discovered Massachusetts infestation 

 is completely flowed every winter to a constant depth of about 9 inches. 

 It has a peat "bottom" with first-class drainage during the growing 

 season. It has been resanded every other year for the past ten years. 

 When it was examined on December 8, most of the grubs were found just 

 below the inch and one-half thickness of frozen surface sand, but they 

 ranged to a maximum depth of 8 inches. 



On September 16 the writer examined a bog in South Carver on which 

 small beetles in great numbers had been for some time devouring the 

 foliage. The infested bog was circular in form and had a total area of 

 about five acres. One and one-half acres in the very middle part had 

 been turned brown by the insect in a way to suggest, to one viewing it from 

 some distance, a severe fire-worm attack. The beetles were mating very 

 freely at the time and were also feeding on the cranberry foliage vora- 

 ciously, the backs of the leaves receiving most of their attention, though 

 the front side was also eaten considerably. A quantity of these insects 

 was collected and preserved, and they have been identified ^ as belonging to 

 the species known to science as Cryptocephalns incertus Oliv. The beetles 

 are from about 2 millimeters to about 3 millimeters (from less than three 

 thirty-seconds to about one-eighth inch) in length, the smallest specimens 

 being males while the larger ones are females. As a rule, they are seal 

 brown in color, though some of the females are almost black. Both sexes 

 have rather conspicuous, though poorly defined, white longitudinal stripes 

 on the wing covers. 



The manager of the infested bog had noticed a considerable injury to 

 the vines as early as the 20th of August, though he did not discover the 

 beetles until a few days before the writer's visit. This fact, taken in 

 connection with the very general mating observed, leads to the suspicion 

 that much of the injury seen by the writer had been caused by the larva 

 of the insect. The infested bog is eighteen years old, has been completely 



1 By Mr. E. A. Schwarz of the Bureau of Entomology of the United States Department of 

 Agriculture. 



