142 INTERNAL ANATOMY OF INSECTS. 
hay. A little gall-fly (Cynips Quercus Ramuli L.) has 
the remarkable odour of Fraxinella: the larva ofanother 
species of this genus (C. Rose) has an odour which 
seemed to Reaumur as attractive to cats as that of Ne- 
peta cataria or Teucrium Marum*: some Phalangia smell 
like walnut leaves’ ; and the various species of the ge- 
nus Prosopis (Melitta * b. k.) have a very agreeable scent 
of Dracocephalum moldavicum”. 
We next come to fetid odours. ‘These in numerous 
cases are known to be secreted and emitted by appro- 
priate vessels and organs; they are often exhaled from a 
fluid secretion, of which, in the letter lately referred to, 
I gave you almost all the known instances. Savi, in his 
history of Zulus factzdissimus, informs us that it emits a 
yellow fetid fluid from its supposed spiracles, which if ap- 
plied in sufficient quantity imparts a red colour to the 
skin, to be removed neither by friction nor washing, but 
only disappearing by time; when removed from the black 
vesicles in which it is stored, it shoots into very trans- 
parent octoedral crystals *. 
I have before mentioned the coloured fluid which some 
insects emit when they are disclosed from the pupa, 
and that it probably exhales some powerful odour which 
attracts the males‘. 
The great Hydrophilus, in its larva state, when first 
taken into the hand remains without motion; in a mi- 
nute afterwards it renders itself so flaccid as to appear 
like a cast skin. ‘Taken by the tail it contracts itself 
considerably, it then agitates itself briskly, and ejaculates 
with a slight noise a fetid and blackish fluid ¢. 
* Reaum. iii, 494, > Mon. Ap. Angl. i. 136. 
© Osservaz. sullo Iulus, &c. 14. * Vor. Til. p. 299. 
© N. Dict. a? Hist. Nat. xv. 487. 
