f>74 



RESPIRATORY APPARATUS OF INSECTS. 



525. The 'Stigmata' or ' Spiracles' through which the Air enters 

 the Tracheal system, are generally visible on the exterior of the 



Fig. 346. 



Tracheal system of Nepa (Water-scorpion) :— a, Head ; b, first 

 pair of Legs ; c, first segment of the Thorax ; d, second pair of 

 Wings ; e, second pair of Legs ; /, Tracheal trunk ; g, one of the 

 Stigmata ; h, Air-eac, 



body of the Insect (especially on the abdominal segments) as a 

 series of pores along each margin of the under surface. In most 



