TRACHEATA 



325 



mouth and anus. The mouth is overhung by the labrum, and 

 has the mandibles and first maxillae on either side; behind 

 it is bounded by the labium or fused second maxillae ; the 

 mandibles cut and crush the food, which is held in position 

 by the maxillae. The passage of the food into the mouth is 

 assisted by a hairy prominence on the anterior surface of the 

 labium. 



The mouth leads into an oesophagus which pierces the 

 nerve mass, and then swells into an inconspicuous crop ; this 



Pio. 187. — View of male Melolontha vulgaris, 

 from which the dorsal integument and heart 

 have heen removed to show the internal 

 organs. After Vogt and Yung. 



1. Cerebral ganglion. 



2. 1st thoracic ganglion. 



3. 2nd and 3rd thoracic ganglion. 



4. Fused abdominal ganglia. 



5. Oesophagus. 



6. Mid-gut. 



7. Small intestine. 



8. Colon. 



9. Rectum. 



10. Malpighian tubules, brown portion, 



with caeca. 



11. Malpighian tubules, distal end. 



12. Tracheae with vesicles. 



13. Testes, opening into coiled vasa 



deferentia. 



14. Penis. 



15. Single vas deferens. 



opens into a brown mid-gut, in which the processes of diges- 

 tion are mainly carried on. The mid-gut passes into a finer 

 tube, the small intestine, which receives the Malpighian tubules, 

 and this in its turn passes into the colon, which has on its 

 inner side six longitudinal muscular ridges ; this opens through 

 the rectum to the exterior. With the exception of the mid- 

 gut, the alimentary canal is lined with a thin layer of chitin, 

 continuous at the mouth and anus with the exoskeleton, and 

 this is cast at the ecdysis of the exoskeleton. In Mdolontha 

 neither salivary glands nor hepatic diverticula are described. 

 The Malpighian tubules are four in number ; they are very 



