14?8 INTERNAL ANATOMY OF INSECTS. 



the remarkable odour of Fraxinella: the larva of another 

 species of this genus (C. Rosa] has an odour which 

 seemed to Reaumur as attractive to cats as that of Ne- 

 peta cataria or Tcucrium Marum a : some Pkalangia 

 smell like walnut leaves b ; and the various species of the 

 genus Prosopis (Melitta * b. K.) have a very agreeable 

 scent of Dracocephalum*moldavicum b . 



We next come to fetid odours. These in nume- 

 rous cases are known to be secreted and emitted by ap- 

 propriate vessels and organs ; they are often exhaled 

 from a fluid secretion, of which, in the letter lately re- 

 ferred to, I gave you almost all the known instances. 

 Savi, in his history of lulus fcetidissi?nus, informs us that 

 it emits a yellow fetid fluid from its supposed spiracles, 

 which if applied in sufficient quantity imparts a red co- 

 lour 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 transparent 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 d . 



The great HydropMlus, 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 e . 



t> 



a Reaum. iii. 494. h Mon. Ap. Angl. i. 136. 



c Osscrvaz. sullo lulus, $c. 14. d VOL. III. p. 297. 



" N. Diet. d'Hist. Nat. xv. 487. 



