23 
At figure 1 11 is seen a convoluted tube, which, in dissecting one 
of these, once presented itself to me, and which I apprehended 
was the alimentary canal or intestine of the Larva. 
On opening the body of the Bot, and removing the gelatinous 
matter, the air tubes are seen, of a splendid silvery colour, or as 
though injected with pure quicksilver. Their appearance is sin¬ 
gularly beautiful, especially if the Bot be alive, or recently dead; 
and it was in reality what first attracted my attention to these 
objects, for if dead, and kept some time, these tubes become dull, 
and of a brown colour. This glittering appearance arises from 
the air being seen through the semitransparent pearly refracting 
coats of the vessel. They remain distended by their owh inhe¬ 
rent elasticity, and are filled with air to their minutest ramifica¬ 
tions. These branches often run up and down in the gelatinous 
matter, in directions nearly parallel to the principal trunk.—See 
fig. 11. 
These tracheae or air pipes are eight in number in this Larva, 
and their disposition is endeavoured to be represented at fig. J. 
The two smaller ones, exterior to the central circle of larger 
ones, appear to communicate with two small prominent nipples 
or points upon the first segment, which are seen in fig. 10. 
These tracheae or air tubes open into one common reservoir, at 
the large end of the Larva, beneath a singular plate, fig. 9, of a 
cartilaginous or horny consistence, having six semicircular lines, 
with their points curved and opposed to each other ; these lines 
are also made up of alternate depressed and elevated spots of 
black and white ; and at this blunt extremity are also seen two 
protuberant lips or sacs, filled with a watery fluid, w hich meet 
and serve to close over and cover up this horny plate.—See 
fig- 8. 
Through this plate the air is perhaps admitted into these tubes, 
the branches of which appear to terminate in the skin, the gela¬ 
tinous matter, and upon the viscera. In most Lame of the fly 
