51 
CHAPTER VIII. 
RESPIRATION. 
Breathing Apparatus — Spiracles — Trache<2 and their Structure 
— Spiral Filaments — Communicatiofi between Trachece — Air 
Sacs — Smaller in Queen — Use of Air Sacs — Specific Gravity 
Altered — Anterior Spiracles the Largest — Bispiration and 
Expiration. 
The bee, like most other insects, does not breathe as 
we do, through apertures in the head, but air is ad- 
mitted by special openings provided for this purpose 
situated on the surface of the body. These openings 
are called spiracles (frontispiece, ^), and there is a row 
of them on each side of the body. They are supplied 
with a mechanism by which they can be voluntarily 
closed, and their structure has been studied and de- 
scribed by many investigators, more particularly by 
Newport (n6), Landois (88), and Krancher (84). 
Each spiracle consists of two openings, one behind 
the other. The inner one can be closed by a valve, 
and the outer one is provided with short hairs along 
the edge of the opening, to prevent dust and other im- 
purities from entering. Their structure will be more 
fully explained when we treat of the voice of the bee, in 
the production of which they play so important a part. 
The spiracles are the openings leading to in- 
ternal tubes, called trachece., which branch in all 
directions through the body of the insect (see 
frontispiece and Fig. 26). 
There are two pairs of spiracles in the thorax, viz,, 
