716 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



distinguished from those of other species by their extreme slenderness, 

 aud being packed with fine white sawdust they resemble a tangled mass 

 of small threads lying upon the surface of the wood. On coming to 

 inspect them particularly, small irregular cavities will be noticed, one 

 of which is represented by a knot-like appearance. This cavity is ap- 

 propriately termed the nuptial chamber by French and German writers. 

 From it there are usually four galleries leading off in opposite direc- 

 tions and running obliquely to the grain of the wood, but curving, com- 

 monly, till they obtain a longitudinal direction. And from these numer- 

 ous smaller and irregular wav^y galleries branch off", at right angles or 

 nearly so, and overspread the whole surface with a seemingly confused 

 multitude of little furrows. The bark being quite thin in the young 

 trees to which these beetles resort, their galleries are excavated mostly 

 in the wood, the surfiice of which is deeply grooved whilst only a shal- 

 low impression is made on the inner surface of the bark. But at the 

 end of each of the lateral galleries a deep cavity will be noticed, sunk 

 in the bark, in which cavities the insects repose during their pupa state. 

 <'The accompanying figure of the tracks of these beetles handsomely 

 illustrates some of the facts which have already been stated above un- 

 der the Wood-engraver bark-beetle, and it may interest the reader to 

 notice some of the habits of these insects as shown by this figure.* In its 

 upper half two leading galleries are seen running parallel with each other 

 and so near together that no adequate space exists between them for 

 any young larvae to form their burrows there without encroaching upon 

 each other or crossing the tracks already made. The parent beetles ap- 

 pear to have been aware of this, and accordingly so disposed of their 

 eggs that all their young with but two or three exceptions mined out- 

 wards, traveling away from each other. Again, on the outer side of the 

 left gallery two notches are observed, in which no eggs appear to have 

 been placed, the parent beetle probably perceiving, what the figure in- 

 dicates, that there was not suitable room to the left of these notches to 

 duly accommodate all of the other larv?e that would traverse that spot. 

 Furthermore, it will be noticed tbat of the burrows leading off to the 

 right, above the large knot or nuptial chamber, the worm which exca- 

 vated the fourth one, soon after commencing his journey, perceived that 

 the course he was pursuing would run his track into that of the third 

 one. He hereupon abruptly alters his course, bearing directly away from 

 the track of this neighbor until he has attained a suitable distance 

 therefrom, aud he then travels forward again, keeping at this exact dis- 

 tance from his neighbor's path. But this soon brings him into prox- 

 imity with another neighbor upon the other side; and he now becomes 

 aware of the fact that he is between two paths that are approaching 

 each other, and that will consequently come so near together forward of 

 him that he can not proceed onward without running into one or the 

 other of them. In this dilemma, to encroach the least that is possible 



Not reproduced. 



