Respiratory Organs. 



55 



placed brahchise, and thfen makes it serve a further turn by 

 forcibly expelling it, when the insect is sent darting ahead. 

 Thus this curious apparatus not only furnishes oxygen, but 

 alsa aids in locomotion. In the pupse of insects there is little 

 or no motion, yet important organic changes are taking place 

 — the worm-like, ignoble, creeping, often repulsive larva, is 

 soon to appear as the airy, beautiful, active, almost ethereal 

 image So oxygen, the most essential — ^the sine qua rum — of 

 all animal food, is still needed. The bees are too wise to seal 



Fig. 11. 



Alimentary Caned. 



o — Honey stomach, 

 c— Urinary tubes. 



6 — True stomach, 

 d— Intestine. 



the brood-cell with impervious wax, but ratljer add the porous 

 capping, made of wax and poUen. The pupse no less than 

 the larvae of some two-wing flies which live in water, have 

 long tubes which reach far out for the vivifying air, and are 

 thus called rat-tailed. Even the pupa of the mosquito, await- 

 ing in its liquid home the glad time when it shall unfold its 

 tiny wings and pipe its war-note, has a similar arrangement to 

 secure the gaseous pabuluni. 



The digestive apparatus of insects is very interesting, and, 

 as in our own class of animals, varies very much in length and 

 complexity, as the hosts of insects vary in their habits. Aa 

 in mammals and birds, the length, with some striking excep- 



