248 



MANUAL OV ZOOLOGY 



/us. Appended to the chyle stomach at its anterior end are 

 in many insects a number of tubular pouches, the hepatic 

 cceca (ctxc). At the junction of the chyle stomach with the 

 small intestine, or further back, there open a number (from 

 2 to over ioo) of narrow tubular appendages, the Mal- 

 pighian tubes (inalp), which are the organs of renal ex- 

 cretion. The intestine is usually 

 elongated, its posterior portion is 

 dilated to form a wide rectum, 

 which opens in the anal aperture 

 on the last segment. Anal glands 

 producing an odoriferous secretion 

 often open into the rectum. 



The organs of respiration are a sys- 

 tem of fine branching tubes, the tra- 

 chea (Fig. 147), which communicate 

 with the exterior through valvular 

 apertures known as stigmata situated 

 at the sides of the segments. These 

 tracheae form a completely ramify- 

 ing system which conveys the air to 

 all the parts of the body. The wall 

 of the tubes is strengthened by a 

 series of spirally wound chitinous 

 ^rf'ttrKm^/i?.: fibres, each fibre or thread making 



lysttT 1 ''(Aft"' 'Mialf^nd fr0m 0ne t0 f ° Ur OT five tUrnS arOUlld 



Denny -' the tracheae. In some insects, mainly 



those adapted for active flight, the tracheal system is dilated 

 in certain parts of the body to form large air sacs. In the 

 aquatic larvae of some insects there is a series of soft external 

 simple or divided processes — the tracheal gills — attached 

 to the abdominal segments, and richly supplied with tracheae 

 which have no communication with the exterior. 



