INSECTS AFFECTING FOREST TREES. 493 



encc goes, since it is one of the forms which revel in partly rotten tissues. I'lie- 

 operations o! this grub and certain associated insects soon hiosen the bark so that it 

 drops off in large sheets. The work of this species is shown at plate 7, figure 4. 



Descriptioi:. This beetle is a grayish insect, mottleil with black and about 

 ^ of an inch long. Its general form and markings are well shown in plate 11, 

 figure 1. Thj prothoracic spines and the two prominent ridges on each wing 

 cover arc the mtjst characteristic features of this beetle. 



The pupa is white, rather stout, and varies in length from about y^, to nearly 

 ^ of an inch. The dorsum of the head, pro- and metathora.x and each abdominal 

 segment bear minute hairs or setae somewhat grouped on each side of the dorsal 

 line. The brown abdominal spiracles are conspicuous. Plate 11, figure 4. 



The pupal cell is constructed just under the bark. It is oval, about 'i by ^ 

 inches in diameter and is partly lined with somewhat decayed wood particles. The 

 .iiost characteristic feature is the mass of fibers torn from the wood at the side of 

 the cell and incorporated in its walls (Plate II, figures 7, 8, 10 and 12). The excava- 

 tion in the wood is probably necessary in order to give requisite depth for the 

 thicker pupa and beetle. This is in marked contrast to the pupal cells of Pvtlio 

 aincricanus Kirby, a species frequently associated with Rhagium and which is 

 noticed on the following page. 



The white flattened grub or larva ranges in length from i-^ to i'^ inches and is 

 remarkable for its broad head, which is amber-colored and is fully as wide as the 

 thoracic segments. The powerful jaws are tipped with black. The corneous pro- 

 thoracic shield is yellowish, and the six true legs are poorly developed (Plate 11, 

 figure 1 1). 



Life History. Some pupae and many beetles were found under the bark of one 

 tree September 21st. The remaining pupae were nearly ready to assume the adult 

 form and the beetles were to be found mostly within the pupal cells. Many of them 

 had begun to burrow in an oblique direction up and out through the bark. Some 

 iiad just startetl the work, but in many cases the beetles had nearly penetrated the 

 thick bark, though none had escaped, so far as was observed. 



The grubs of this species evidently become full grown during the latter part of 

 the summer, construct their pupal cells, and transform to beetles before the 

 approach of cold weather. The adults winter very largely in the pupal cells or in 

 the characteristic upward, curving exit burrows which they begin soon after assum- 

 ing the ailult condition. 



