60 INTERNAL ANATOMY OF INSECTS. 
dissecting a species of Noctua related to N. Pronuba, 
but I do not recollect the particular species,—at the base 
of the abdomen of the male I discovered two bunches 
of long fawn-coloured parallel hairs, planted each in an 
oval plate, plane above, but below convex and fleshy ; 
while the plates remained attached to the insect, they 
appeared to have a distinct pulsation. The hairs, which 
are about half an inch long, diverge a little, and form a 
tuft not very unlike a shaving-brush?. I have not 
since met with this species, but I have preserved the 
brush and scale. Somewhere in Bonnet’s works, but I 
do not recollect where, I have since found mention of a 
similar fact in another moth. 
II. Having considered the external respiratory organs 
of insects, by which the air is received, we are next to 
consider the znternal ones, by which it is distributed. 
These are gills; trachee and bronchie ; and sacs or 
pouches, 
i, Gills (Branchie*.) Waving lately described what 
may be denominated false gills, or branchiform ap- 
pendages, I shall now call your attention to what may 
be denominated true ones, which are peculiar to the 
Arachnida Class: but what is remarkable, the animals 
that breathe by them are very rarely inhabitants of the 
water, so that their functions cannot be perfectly analo- 
gous to those of fishes. 
In the Scorpion, on each side of the four first ventral 
segments a spiracle may be discovered, which has no 
4 Prate XXIX. Fic. 21. » Marcel de Serres (Mem. 
du Mus. 1819. 137, &c.) calls the tubular trachee that receive the 
air, arterial trachea, and the vesicular ones, which act as reservoirs, 
pulmonary trachea. * Prate XXIX, Fic. 1. 2. 
