136 HOW INSECTS BREATHE. 



for. It is probably in part owing to the want of popular 

 works on anatomy. At present the young Entomologist, 

 who wished to know something more about the structure of 

 the insects which he collects, than their outer form and colours, 

 would probably, unless some one was near to inform him, 

 have great difficulty in obtaining any suitable book ; and if, 

 without profiting by the experience of his predecessors and 

 trusting boldly to his own exertions, he endeavoured to solve 

 the question for himself, he would, when he had removed the 

 skin of any insect he might choose as most suitable for his 

 purpose, find before him an intricate and apparently confused 

 labyrinth of nerves, tubes and vessels — a sort of Gordian knot, 

 more easy, alas, to cut and spoil, than to unravel ; a little 

 microcosm, showing, as has been said of our earth itself — 

 " no trace of a beginning, no sign of an end." 



If, however, the insect be fresh, one set of tubes, distin- 

 guished by a silvery white colour, will be seen running over 

 and among the other organs, like the roots of a tree in 

 the earth ; these are the tracheae or air tubes, part of the 

 breathing organs, of which it is my object here to give a 

 short account. I shall not attempt to describe these organs 

 in detail, but shall only notice them very briefly, and then 

 point out some of the chief differences, and especially such 

 as bear reference to the habits of the insect. For convenience 

 of description we may divide the respiratory organs of insects 

 into two parts, the spiracles or breathing holes, and the tra- 

 cheae or air tubes.* 



The body of an insect consists of thirteen rings. The first 

 forms the head; the next three are called the prothorax, 



* The most complete account hitherto given of these organs is 

 in Burmeister's Handbook of Entomology, which was translated by 

 Shuckard in 1836, and in which will be found references to the earlier 

 works on the subject. 



