142 PINE, 
the mother gallery of the Pine Beetle, one of which (here reproduced) 
I had carefully figured, so that it gives a very correct representation 
of the gallery, natural size and magnified. 
These figures show how the flow of turpentine, now hardened into 
an irregular coating, has stopped development of the young maggots, 
though, if carefully examined, the figure shows in places the little 
niches of commencement of attack along the sides of the gallery. 
This point (of the flow of sap checking development of attack) is of so 
much practical interest, that I wrote further on the subject to Dr. 
Mother galleries of H. piniperda beneath Larch bark, natural size and magnified. 
From Dr. Somerville’s specimens. 
Somerville, who kindly replied to me as follows :—‘‘I delayed answering 
your letter till I had made another examination of the Larch trees, 
and I am now able to answer your questions fully. The trees which 
were attacked by H. piniperda were taken possession of by great 
numbers of this insect, which laid its eggs in little niches as usual ; 
these in due course hatched out, and the larve proceeded to eat into the 
bast, but the resin had proved too much for them, for in no case (at 
least in no case that I have observed) did they develop into beetles.” 
For the information in evtenso the reader is referred to Dr. Somer- 
ville’s paper, as before mentioned; but the attack is one of such 
rarity, and also of such curious interest as showing how the flow of 
sap is unsuitable for egg deposit (as alluded to at p. 140), that I have 
repeated some of the chief points. 
