INSECTS AFFECTING PARK AND WOODLAND TREES 349 



of the wood, indicating- that this species burrows very largely in the inner 

 bark. The work of this insect is sometimes inconspicuous. Plate 56, 

 fi(jure 2, shows the base of a tree, the inner bark of which has been 

 thoroughly riddled by this borer, as shown on plate 56, figure 3, while it 

 will be seen that nothing but decaying borings lies between the outer bark 

 and the surface of the wood. The few exit holes on such a tree are shown 

 on plate 56, figure 1. The galleries of this insect are sometimes preserved 

 for indefinite periods and constitute unimpeachable records of injury to 

 living trees. Plate 55, figure 4, shows an elongated piece of bark with a 

 series of longitudinal well preserved burrows which have been kept from 

 injury by insects usually following Tomicus because their walls were infil- 

 trated with pitch, conclusive evidence that the tissues were living at the 

 time this bark borer attacked the tree. The same thing is shown more 

 plainly in plate 56, figure 2. It will be observed that the burrows on either 

 side of these preserved channels have been almost entirely obliterated by 

 insects which follow the original invaders. Plate 60, figure 4 shows how 

 the Tomicus burrows may be obliterated by R h a g i u m 1 i n e a t u m Oliv., 

 a species living in decaying bark. The work of this scolytid in con- 

 junction with other forms to be noticed later is well shown on plate 53, 

 figure 1, which represent two pines photographed Sep. 28, 1901. It will 

 be observed that the tip of one has very little foliage and as a matter 

 of fact it was entirely dead at that time. The lower limbs, however, were 

 thrifty and green and though insects were working in the trunk the tree 

 still appeared to be vigorous. The other tree in the photograph bears 

 rather abundant foliage and showed very little evidence of weakness, though 

 it was somewhat injured at that time by the borers. The same trees are 

 represented at figure 2, as they stood Ap. 28, 1902. It will be observed 

 that the tree with a dead tip the preceding September has been entirely 

 killed and that very few needles are to be seen on the other one. which 

 showed comparatively little injury the preceding fall. Both are dead and 

 are evidences of the rapidity with which this insect and its associates may 

 work. Plate 52 shows a somewhat familiar condition in the vicinity of 



