Respiratory OrganK. 



55 



placed branchios, and then makes it serve a further J;urn by 

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

 Thus this curious apjiaratus not only furnishes oxygen, but 

 also aids in locomotion. In the pupre 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 

 imago.^ So oxygen, ■ the most essential — the sine qua non — of 

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



Alimentary Can 



o— Honey stomach. 

 c — Urinary tubes. 



-True stomacl). 

 -Intestiue. 



the brood-cell 'with impervious wax, but rather add the porous 

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

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

 long tubes which reach fkr 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 pabulum. 



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. As 

 in mammals and birds, the length, with some striking escep* 



