BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS 167 



are given off branches, which in turn repeatedly subdivide, 

 until all parts of the body are ramified by tracheae, large 

 and small, bringing air to all the tissues. The oxygen is 



brain 

 oesophagus 



muscles 



.....crop 



elytron 



alimentary 



canal 



ventral nerve 

 chain 



wing 



. , ,, %. \ '^ N . Malpighian 

 accessory glands^' fectum ^L\ ^Jr *' intestine tubules 



\receptaculum~seminalis 



FIG. 40. Dissection of female great water-scavenger beetle, Hydrophilus 

 sp., the heart and tracheae being cut away. 



taken up from this air, and carbonic-acid gas is given up 

 to it, when it passes out of the body again through the 

 spiracles. Thus in the insects oxygen and carbonic-acid 



