348 ORGANS OF DIGESTION. 



terior part of this lower lip forms the mentum, and its soft 

 anterior portion supports the fleshy prominent tongue. The 

 masticating organs present infinite varieties of form accord- 

 ing to the difference of food in insects, as in other classes of 

 animals, but the same constituent parts of the mouth can 

 be recognized in all the different forms of mandibular and 

 haustellar apparatus. The same buccal organs form broad, 

 short, and strong cutting instruments, which move trans- 

 versely, in those insects which subsist on hard food, and 

 a long, slender, tubular apparatus, capable of extension and 

 retraction, in those, which suck fluid or soft substances. 

 These parts often change from the one form to the other in 

 the same insect, while it changes its kind of food in the pro- 

 gress of its metamorphosis ; and where the food is the same 

 in the larva and imago, the masticating organs preserve the 

 same form in these two conditions of the insect. The food 

 reduced by the mandibles and maxilla and mixed with the 

 secretion of one or more pairs of salivary glands, is trans- 

 mitted by a pharynx of variable length, to the oesophagus 

 and alimentary canal. The oesophagus commences by a 

 narrow canal which generally forms an enlargement of crop 

 at its lower part, for receiving and collecting the food when 

 first swallowed ; this enlargement of the oesophagus is often 

 covered with minute short glandular follicles which open 

 into its interior. Below the crop is a small but strong mus- 

 cular gizzard, with thick parietes, and provided internally 

 with numerous longitudinal rows of hard sharp conical horny 

 teeth. This muscular triturating stomach is most developed 

 where the hardness of the food most requires its aid, as in 

 most of the orthopterous and coleopterous insects ; but 

 where the food is liquid, as in most of the sucking hemiptera, 

 the gizzard is scarcely perceptible. The largest, the most 

 constant, and the most important gastric cavity in insects, 

 is the long, wide and highly glandular chylific stomach which 

 extends generally from the gizzard to the insertion of the 

 hepatic ducts. The chylific stomach is, for the most part, 

 amply furnished with considerable glandular follicles, which 

 are developed from its whole parietes, arid open by separate 

 orifices into its interior. This cavity is frequently of great 

 length, and partially divided by numerous transverse con- 

 strictions, it is then most wide and glandular at its anterior 



