244. MEANS OF DEFENCE OF INSECTS. 
(M. cynipsea, L.) emits a fragrant odour of baum*.—1 
have not much to tell you with respect to apterous insects, 
except that Julus terrestris, a common millepede, leaves a 
strong and disagreeable scent upon the fingers when 
handled». Most of the insects I have here enumerated, 
probably, are defended from some enemy or injury by the 
strong vapours that exhale from them; and perhaps some 
in the list produce it from particular organs not yet noticed. 
I shall next beg your attention to those insects that 
emit their smell from particular organs. Of these, some 
are furnished with a kind of scent-vessels, which I shall 
call osmateria; while in others it issues from the intes- 
tines at the ordinary passage. In the former instance the 
organ is usually retractile within the body, being only ex- 
erted when it is used: it is generally a bifid vessel, some- 
thing in the shape of the letter Y. Linné, in his gene- 
ric character of the rove-beetles (Staphylinus), mentions 
two oblong vesicles as proper to this genus. These or- 
gans,—which are by no means common to the whole ge- 
nus, even as restricted by late writers,—are its osmateria, 
and give forth the scent for which some species, particu- 
larly S. brunnipes, are remarkable. If you press the ab- 
domen hard, you will find that these vesicles are only 
branches from a common stem; and you may easily as- 
certain that the smell of this insect, which mixes some- 
thing extremely fetid with a spicy odour, proceeds from . 
their extremity.—A similar organ, half an inch in length, 
and of the same shape, issues from the neck of the cater- 
pillar of the swallow-tail butterfly (Papilio Machaon, LS, 
‘When I pressed this caterpillar, says Bonnet, near its 
* De Geer, vi. 135. 33.» Ibid. vii. 581. © Pare XTX. Fic. I... 
