334 ^'E\V VOKK STATE MUSEUM 



diverging somewhat sinuous larval galleries which run approximately trans- 

 versely of the wood fibers. This is the work of a large borer known 

 as Tomicus calligraphus Germ., an insect that occurs in the 

 thicker bark of trunks and larger limbs of both hard and soft pines. 

 It normally does not caLise very much injury bu;; under exceptional con- 

 ditions it may become so abundant as to kill a tree very rapidly, so much so 

 that the writer has known young pines, in apparently excellent condition, 

 killed in lo weeks' time. These borers sometimes become so abundant 

 as to eat away practically all of the inner bark, a condition represented at 

 plate 56, figure 3. 



Farther up on the tree in the thinner bark of the trunk and the medium 

 thick bark of the larger limbs, a smaller species may be found at work in 

 some pines and its method of operation is well shown in plate 60, figure 3, 

 which represents the longitudhial burrows and the larval galleries of this 

 smaller species, Tomicus cacographus Lee. This is a very badly 

 infested piece of bark and plate 60, figure 2, illustrates the work of this 

 insect on limbs of hard pine which it had entered in the fall of 1900. It 

 will be observed that these galleries are very irregular and anastomose with 

 out apparent reason. These are evidently galleries which the beetles have 

 made for feeding purposes and in which they pass the winter. 



Higher up on a white pine in the still thinner bark of the smooth 

 trunk; a smaller form, the pine bark beetle, T o m i c u s p i n i Say, may be 

 observed at work. This species operates not only in the trunk but also in 

 the medium thick bark of the smaller limbs and not infrequently attacks liv- 

 ing tissues. Plate 59, figure i, which is from a photograph taken with a 

 light background, represents the numerous exit holes which this species 

 may make in a badly infested section of a trunk and also a number of small 

 pitch tubes and plate 59, figure 2, shows the inside of the same piece of 

 bark photographed in a similar manner. The method of operation of this 

 soecies is well illustrated, the central chambers, the primary galleries and 

 the dilating mines of the young together with larger flat tortuous mines 

 of another species known as the pine sawyer, M o n o h a m m us c o n- 



