1908 ENTOMOLOGICAL SOCIETY. 25 



all, we occasionally find a piece of fossilized wood engraved by one of these 

 borers. We have before us an illustration representing a piece of arbor 

 vitse from the interglacial beds in the vicinity of Toronto, and the carvings, 

 though faint, tell interesting stories of earl^ life on this continent. The 

 form of these galleries is so characteristic that Dr. Hopkins, our American 

 authority on this group, referred the maker {Fhloesinus squahdens, Scudd.) 

 to a genus and on account of the restricted food habits of its allies, gave a 

 provisional determination of its food plant. The Ash Bark-beetle (Hylesinus 

 aculeatus, Say) presents another type, since the adult galleries diverge from 

 a common point, indicating, as we are told, that two females are probably 

 responsible for their construction. The borings are beautiful in their 

 regularity. 



Some of these insects are very injurious to our forest trees, and a study 

 of their habits has therefore a practical, as well as a scientific value. It is 

 interesting to note what can be learned from a large pine tree which has 

 evidently been dead some years. The bark may have largely disappeared, as 

 in the case illustrated, but a close examination of the lower portion of the 

 trunk shows that the sapwood has been badly scored by some borer, and a 

 little familiarity wiih. the habits of these insects would enable us to name the 

 offender. Before attempting this, let us look at the condition of two pines 

 as they were in September. One is apparently in excellent condition while 

 the top of the other has perished. The needles of both, though not shown in 

 the illustration, were decidedly unhealthy and by the following spring the 

 trees were bare and the bark had begun to peel. An examination of the lower 

 portion of the trunk shows a number of pitch tubes, indicating clearly that 

 certain bark beetles had been at work before life was extinct. A pitch tube 

 is nothing more than particles of pitch carried by the insects from their 

 burrows and laid around the mouth of the exit. The insect responsible for 

 this work is known as the coarse writing bark beetle {ToTuicus calligraphus. 

 Germ.), a species which makes a very characteristic series of galleries and 

 confines its operations almost exclusively to the thicker bark of the lower 

 portion of large trees. Occasionally a dead tree may be found standing and 

 give little external evidence as to the cause of injury, A closer examination 

 may result in finding circular exit holes here and there upon the bark. These 

 invariably mean that insects have been at work beneath. The' removal of a 

 large piece of bark may reveal a confused mass of galleries frequently nearly 

 filled by borings and decaying particles of bark. Apparently there is little 

 of significance, but on brushing away the debris, we sometimes find a few 

 galleries preserved by infiltrated pitch, incontrovertible evidence that the 

 pine was attacked while alive. The tree, in making an effort to recuperate 

 from the injury, exudes pitch. This latter infiltrates the walls of the 

 galleries and thus a record of injury may be preserved for years. The bark 

 borer is followed in turn by certain species which live upon the dead inner 

 bark, and in some instances also upon dying" wood. One of the most charac- 

 teristic of these is Rhogium lineaturn,, Oliv., a species which produces, 

 between the bark and the wood, very characteristic pupal cells, the walls of 

 the latter being composed largely of white fibres torn from the sapwood. 

 Pytho americanus, Kirby, is an ally of the same and, like its associate, 

 constructs between the bark and the wood a distinctive pupal cell, the walls 

 of the latter being composed entirely of almost rotten bark borinsrs. The two 

 last named snecies may also be founri in association with Monohammus, the 

 larvae of which are perhaps better known as sawyers. The exit holes of 

 Monohammus are larsre, irregiilar. not sharply defined. The galleries made 

 by the larvae are easily recognized, since they are broad, irregular, traverse 



