JOURNAL OF PROCEEDINGS. 
lxxxiii 
The following observations by Mr. Sells on the perforations of 
the larvae of Sirex juvencus, were omitted in the Journal of Pro- 
ceedings of the 1st of February, 1836, and are here introduced 
in connexion with Mr. Ingpen’s remarks on Sirex duplex : — 
“ In tracing the mining operations of the larva of Sirex juvencus 
in the small sample of the wood submitted to my examination, 
they appear to be mainly carried on in a zig-zag manner ; the in- 
sect proceeding either in a straight course with the fibre of the 
wood, diagonally, or tortuously, according to the texture it has to 
deal with, to the extent of an inch and half or two inches ; it then 
eats its way transversely, and that very wisely only for a space 
just sufficient to allow of its turning round, when it advances about 
the same distance as at first, turns again and so on. 
“ The firmly compacted substance which completely fills the 
cylindrical passages formed by tbe insect, I apprehend to be its 
excrementitious rejectamenta ; it is almost entirely composed of fine 
wood powder, is quite uncoloured by the secretions of the larva, 
and can admit but a very small supply of air for respiratory pur- 
poses. 
“ The pieces of wood which I have seen have all the perforations 
of the same size, as though formed by insects of the same bulk. 
“Messrs. Kirby and Spence, when speaking of the indirect 
injuries caused by insects, confine their remarks on this subject to 
saying — ‘ Mr. Stephens informs me that the fir-trees in a plantation 
of Mr. Foljambe’s in Yorkshire, were destroyed by Sirex gigns, 
while those of another belonging to the same gentleman in Wilt- 
shire met with a similar fate from Sirex juvencus.’ Now as it is 
always desirable to unite the utile with the dulce in scientific in- 
quiries, and we should grant fair attention to the popular question 
of cui bono in these matters, it is worth while to inquire into and 
endeavour to trace out the whole history of this mischievous borer; 
and first, of the places and seasons wherein the female Sirex de- 
posits her eggs, as it is probably in that state only that the enemy 
would be practically assailable, and its course of destruction be 
arrested. 
“It occurs to me that the young larvae may feed upon the albur- 
num, or soft parenchymatous parts of the inner bark, and thus in 
fact do more injury to the tree as regards its vitality than when it 
afterwards operates upon its solid internal parts. Upon these sub- 
jects it is not unlikely that some members of the Society may afford 
satisfactory information.” 
Mr. Westwood, in reference to the remark made by him at the 
