THE BREATHING APPARATUS
Insects do not breathe by means of lungs as we do but through tiny
air-holes, called “spiracles.” This name comes from the Latin
_spiraculum_, meaning an air-hole, which in turn is derived from
_spirare_, to breathe.
Crawling insects do not need nearly so much air as flying insects, and
so their breathing apparatus is not so large. In the bee the breathing
tubes spread over almost the whole body, two of the largest extending
along each side of the abdomen. The rings of the abdomen slightly
overlap one another, and if you watch a bee carefully you will notice
that they are constantly slipping in and out, like the joints of a
folding telescope which is being opened and closed. This is really the
action of breathing, and the bee draws in and then drives out air. If
you have ever rescued a fly which has fallen into the milk, you will
remember that it at once commences to clean itself vigorously with its
legs. It does not do this to make itself tidy, but to clean out the
milk which clogs its air-tubes and is thus choking it.
It is interesting to notice that the mouth of each air-tube has a
number of tiny hairs; these serve to keep out dust, which would
interfere with the breathing. The air-tubes branch off one from
another like the roots of a tree, and in order to give you some idea
of how very small they are, I may tell you that it has been found that
a bundle of a quarter of a million of them would hardly be any bigger
than an ordinary human hair!
[Illustration: PLATE XIII
(_a_)
Photo-micrograph by] [E. Hawks
Sting of Bee
(_b_)
Photo-micro. by] [E. H.
Sting, showing Barbs]