71l> FIFTH KKPORT OF THE I.NTOMOLOGICAL COMMISSION. 
distinguished from those of other species by their extreme sleuderuess, 
ami 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 Freneh and German writers. 
Prom 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 wavy 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 surface 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, iu 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.* Iu 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 larva} 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, iu which no eggs appear to have 
been placed, the parent beetle piobably 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 larvrethat would traverse that spot. 
Furthermore, it will be noticed that 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, and 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 auother neighbor upon the other side; and he now becomes 
a ware 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. 
