74 INTERNAL ORGANS. 



chafer, for example, they are very small and very 

 numerous; but comparatively large in grasshoppers 

 and crickets. In these insects, the air cells can be 

 easily counted. It would be a difficult matter to in- 

 flate them with air, had there not been an ingenious 

 contrivance to facilitate this, in a sort of ribs with 

 which their sides are provided, discovered by Marcel 

 de Serres, and consisting of small projections from the 

 edge of each ring of the belly, and not distinct jointed 

 members. 



The breathing apparatus in the Praying Mantis, showing the 

 numerous air tubes and air cells on each side. 



