THE ANATOMY OF INSECTS. 



APPENDAGES OF THE THORAX. 



17. Leg. 



1 8. Wings. 



19. Pro-legs. 



20. Cerci. 



APPENDAGES OF THE ABDOMEN. 



21. Caudal setae. 



22. Claspers. 



23. Ovipositor. 



24. Sting. 



25. Honey-tubes. 



THE INTERNAL ANATOMY OF INSECTS. 



In order to obtain a clear idea of the relative positions of the 

 different systems of organs in the body of an insect, let us recall 

 the type of the Arthropoda described in the Introductory Chapter. 

 A diagrammatic representation of this type is given in Fig. 36. 



FIG. 36. Diagram of structure of Arthropoda. 



The body-wall is a hollow cylinder ; within this the viscera are 

 arranged as follows : The alimentary canal is central ; the greater 

 part of the nervous system, ventral ; and the circulatory system, 

 dorsal. To this simple conception it will be necessary to add a 

 complicated respiratory system, not possessed by the lower Arthro- 

 pods, and the muscular system and organs of reproduction, the dis- 

 cussion of which was omitted from the Introductory Chapter. 



The Internal Skeleton. Although the skeleton of an insect is 

 chiefly an external one, there are prolongations of it into the body- 

 cavity. As these form support for various organs, and attachment 

 for many muscles, they are often described as the internal skeleton. 



