RESPIRA TION. 
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corresponds to each inspiration and their contraction 
to expiration. 
Vogel (i66) says when a bee is quiet it takes three 
to five inspirations, then the abdomen remains still for 
two to three minutes, and then the rings expand again 
three to five times in a second, again to rest for two 
to three minutes. Young bees, when they first fly 
out, take more inspirations, which are also much 
more rapid, so that it is difficult to count them. 
When the insect prepares for flight, at the mo- 
ment of elevating its wings the anterior pairs of 
spiracles are opened in the act of inspiration, and the 
air rushing into them passes into the tracheae of the 
whole body, distending the air sacs, and rendering 
the insect of less specific gravity, so that when the 
spiracles are closed, at the instant when the bee en- 
deavours to raise itself in the air, it is enabled to 
sustain a long and powerful flight with but little ex- 
penditure of muscular power. In Fig. 21, at are 
shown the air sacs in the thorax surrounded by the 
powerful muscles. 
Newport (i 16) found that the quantity and rapidity 
of respiration has some relation to the muscular power 
of the insect in a state of activity. In a normal state 
he found the inspirations to seldom exceed forty 
per minute, whereas he counted from no to 160 con- 
tractions of the abdominal rings per minute when the 
insect had been much fatigued. 
