DIGESTIVE ORGANS. 



23 



d """" 



the mouth is furnished with a long trunk 

 (fig. 11, d) rolled spirally, composed of 

 two filaments hollowed into a gutter on the 

 internal side, which are in fact the jaws 

 excessively elongated and modified in form. 

 At the base of this tube, we observe in front 

 a small membranous piece which is the 

 representative of the labrum, and, on each 

 side, a small tubercle, the last vestiges of 

 the mandibles. We also perceive in the 

 same situation the rudiments of the maxil- 

 lary palpi (e), and behind we find a little 

 triangular lip bearing two very long labial 

 palpi, composed of three articulations, al- 

 most always hairy and furnished with scales. 



44. The digestive tube (fig. 12) is always open at both ends, 



Fig. 



11. BEAK OP A 



BUTTERFLY. 



Fig. 12. DIGESTION OF INSECTS. 



and extends from the mouth 

 to the anus ; sometimes it is 

 straight, at others, more or 

 less flexuous; and here, as 

 in animals of a higher order, 

 it is very short in carni'vor- 

 ous insects, and very long in 

 those species which feed on 

 vegetable substances. Some- 

 times it preserves nearly the 

 same diameter throughout its 

 whole length ; but, generally, 

 it presents enlargements and 

 contractions which enable us 

 to distinguish an oesophagus, 

 a stomach and an intestine. 

 Sometimes we find several 

 stomachs (/, g, h) which 

 have been named, crop, giz- 

 gard, and chyll'ferous ven~ 

 tricle. 



45. On each side we see 



Explanation of Fig. 11. Beak of a butterfly ; a, the head ; 6, antenna ; 

 c, the eye ; d, proboscis or trunk spirally rolled ; e, rudiment of maxil- 

 lary palpi. 



Explanation of Fig. 12. Digestive apparatus of an insect; a, the head, 

 6, the antennae ; c, the mandibles ; d, the palpi ; c, the oesophagus ; 

 /, g, h, the stomachs ; i, the intestine ; j, the rectum ; k, the biliary vea. 

 sels ; I, secreting organs ; m, the anus. 



44. What are the characters of the digestive organs in insects? For 

 what is the digestive tube of earni'vorous insects remarkable ? Of what 

 parts do the digestive organs consist ? 



45. What are biliary vessels ? 



