386 



ARTICULATA : IXSPTTA. 



air-lioles, called stigmata, arranged along the sides or pos- 

 terior part of the body ; some kinds, however, effect respi- 

 ration by means of lung-like cavities in the body. 



Respiratory apparatus of an Insect Water Scorpion, enlarged. 



ft. head : f 1 , f 2 , f 3 , base of first, second, and third pair of feet ; t, first ring of ttnc 

 thorax ; w. base of wings ; av. agrial vesicles ; tr, trache* ; st, stigmata. 



As in all other articulated animals, the alimentary 

 canal of Insects occupies the central line of the body, and 

 above it is the dorsal vessel or so-called heart (Fig. 354). 



