INSECTS. 



Fig. 69. RESPIRATORY SYSTEM IN NEPA (MAGNIFIED). 



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 trachea3, a character 

 whereby these tubes may be readily distinguished." * 



Fig. 69. a, Head b, First pair of legs. c, First segment of thorax. <?, Base 

 of wings. e, Second pair of legs. e f , third pair of legs./, Tracheae. g, Stig- 

 mata or spiracles. h, Air Bacs. 



* Outline of the Animal Kingdom, by Professor Eymer Jones, p. 2G6. 



