INDIRECT INJURIES CAUSED BY INSECTS. 123 
It would occupy too much space to notice in detail all the bark-boring 
peetles which attack the various species of pine and fir trees, which are very 
numerous, comprising Tomicus pinastri, Laricis, micrographus, typographus, 
and chalcographus (which I found in 1837, in the larva, pupa, and imago 
states, in the bark of Norway fir masts imported to Southampton), Hylurgus 
iniperda, as well as two large weevils, Pissodes notatus and pini, which 
have similar habits, &c. &c. ; and I will conclude the list with stating as 
a sample of the whole the ravages committed by one of the tribe, Tomicus 
typographus, in Germany, where it sometimes attacks the inner bark in 
such vast numbers, 80,000 being sometimes found in a single tree, that it 
is infinitely more noxious than any of those that bore into the wood ; and 
such is its vitality, that though the bark be battered and the tree plunged 
into water, or laid upon the ice or snow, it remains alive and unhurt. ‘The 
leaves of the trees infested by these insects first become yellow; the trees 
themselves then die at the top, and soon entirely perish. Their ravages have 
long been known in Germany under the name of Wurm trikniss (decay 
caused by worms); and in the old liturgies of that country the animal 
itself is formally mentioned under its vulgar appellation, “ The Turk.” 
ous transparent eel-shaped vermicles, not easily visible to the naked eye from their 
small size, being not more than one eighth or one tenth of a line in length, but per- 
ceptible through a pocket lens, especially when exposure to the air or the warm 
breath had made them elevate their tails (or heads, whichever they may be), a 
movement which sometimes takes place speedily, but at others only after a consider- 
able examination, when they present the appearance of so many animated hairs 
twisting and curling themselves in various directions. ‘These vermicles, under M. 
Wesmael’s powerful compound microscope, with which he was so good as to assist 
me in examining them, exhibit not the slightest trace either of mouth or other ex~ 
ternal organ, nor of intestines, nor of internal vessels of any kind, which, if any such 
existed, might be easily seen through their transparent skin and body. This absence 
of all appearance of external and internal organs (the inside of the body seeming 
filled with granular molecules), added to their shape, which is filiform and very 
slender, sharply attenuated at each extremity, and their hyaline colour, with very 
indistinct traces under a high magnifying power of about twenty segments, each as 
long as broad, are all the characters they afford. ‘These characters, or rather nega- 
tion of characters, might perhaps suffice to bring these vermicles under the genus 
Vibrio as formerly extended by Miiller and Bory de St. Vincent (to which, from 
their resemblance to the so-called vinegar eels, Vibrio anguilla, 1 at first referred 
them), but scarcely as it has been recently restricted by Ehrenberg, especially as all 
his species of this genus (Vibrio) reside in water. From their connection with an 
animal, they might be regarded as referable to the Oxyuri, were it not that neither 
my own nor M. Wesmael’s close examination could ever discover any trace of their 
existence in the interior of either the larva, pupa, or imago of Scolyius. Their 
wholly exterior habitat seems also to exclude them from coming under Professor 
Owen’s genus Trichina, of his group Protelmintha, which, from its shape and sim- 
plicity of structure, might possibly include them, but which inhabits the cellular 
tissue between the muscular fibres, enclosed in a cyst in which it lies coiled up. 
Leaving it to future examination to decide the true genus and relations of these 
vermicles, I shall here merely observe, in addition to what has been above said, that 
I have found them upon a large proportion of the pups of Scolytus destructor, and 
Mle oa on some of the lary in an advanced stage of growth, and also on the 
pupe of Hylesinus fraxini; and in such distant localities, and at such different 
periods of the year, that I am persuaded that their occurrence was not accidental, 
but that they are true external parasites, of the family of Scolytide in the pupa 
(and partly in the larva) state, in which, however, they do not seem materially to 
injure them, nor prevent them from becoming perfect insects. (See Spence in 
rans, Ent. Soc, Lond. ii, proc. XV-) 
