INSECTS. 



35 



Fig. C9.— Rbspiratory Systkm in Nepa (magmified). 



is interposed, so as to form, by its revolutions, a firm 

 cylinder of sufficient strength to insure the calibre of the 

 vessel from being diminished, but not at all interfering with 

 its flexibility or obstructing its movements; and this fibre, 

 delicate as it is, may be traced with the microscope even 

 through the utmost ramifications of the trachea;, a character 

 whereby these tubes may be readily distinguished."* 



Fig. 69.— a. Head — A, First pair of legs — c. First segment of thorax d. Base 



of wings.— c, Second pair of legs — e', third pair of legs.—/. Trachoffi.— y, Stig- 

 inata or spiracles. — A, Air sacs. 



• Outline of tJie Animd Kingdom, by Professor Kymer Jones, p. 2C6. 



