54; INTERNAL ANATOMY OF INSECTS. 
other instances, proceed to the end, and terminate in 
the two spiracles mentioned above : he conjectures that 
when the animal has occasion to push forth its respira- 
tory apparatus, it injects into these vessels part of the air 
contained in the body of the trachea, which of course 
would cause them to unfold and push forth the tube a . 
When this insect assumes the pupa, instead of its anal 
respiratory organ it has Jour respiratory horns in the 
trunk near the head b . 
The larva of the chamaeleon-fly (Stratgomis Chamce- 
Icon) is furnished with a respiratory organ of a still dif- 
ferent and more elegant structure, exhibiting some re- 
semblance to the tentacida of what are called sea ane- 
monies. In this larva the last joint of the body is ex- 
tremely long, and terminates in an orifice to receive the 
air, which is surrounded by a circle of about thirty di- 
verging rays, consisting of beautifully feathered hairs or 
plumes c . This apparatus serves the same purpose with 
that above described of the larva of the gnat. The fea- 
thery hairs are so prepared as to repel the water, and 
thus to suspend the animal by its tail at the surface, and 
preserve a constant access of air. When it has occasion 
to sink, it turns these hairs in and shuts the orifice, 
carrying down with it an air-bubble that shines like 
quicksilver, and which Swammerdam conjectures enables 
it again to become buoyant when it wants to breathe d . 
In the red aquatic larva of a small gnat (Chironomus 
plumosus) there are two anal respiratory subcylindrical 
horns, with the orifice fringed with hairs e ; and in an- 
a Reaum. iv. t. xxx./. 447—. "' Ibid. 450. /. xxxi./. 1—7. 
c Plate XIX. Fig. 13. a. d Bibl. Nat. ii. 44. 
r Plate XIX. Fig. 10. a. 
