CONTENTS 



Page 



Introduction i 



I. The head 5 



II. The feeding apparatus 7 



Mandibles 7 



Maxillae 9 



Hypopharynx and the cibarium 9 



Labium 1 1 



Evolution of the feeding mechanism i6 



Metamorphosis of the labium 17 



III. The alimentary canal 19 



IV. The thorax 20 



V. The abdomen 24 



Summary 35 



References 36 



