14 DESCRIPTION OF PARTS. 



canal open at each extremity, with an enlargement or dilatation more or less in its central 

 portion ; whence it is diminished, and becomes tubulai and folded repeatedly upon itself, 

 increasing thereby in length until in some instances it is many times the length of the body. 

 Different portions of tins canal have received different appellations, as is highly proper, 

 from the fact that certain of its parts perform functions of a modified character, although 

 all contributing to one general result. In this division of parts, comparative anatomists 

 have employed the same names that have long been in use in the anatomy of the higher 

 animals, as the following enumeration will show, to wit : the pharynx, oesophagus, crop, 

 gizzard, stomach or chylific ventricle, small intestines, cjeciun and rectum. 



Tiie pharynx is the anterior portion or beginning of the canal. The cavity of the mouth 

 opens into it, and it is an aperture more or less enlarged : it is, however, better developed 

 in those insects which masticate their food, the mandibulated class. Indeed it is regarded 

 as having no existence except in this class ; for in the suctorial insect, the next part, or 

 esophagus, is in direct continuity with the haustella or sucking tube, which is connected 

 with it by two distinct tubes. 



The esophagus, commonly known as the gullet, is a tube connecting the pharynx with 

 the crop, or first enlargement of the intestinal canal. It passes directly through the thorax 

 and constricted part of the insect, terminating in the abdomen in the crop. It is variable 

 in length : it may form one-half the length of the canal, while in other instances it is less 

 than one-sixth of such length. It has a peculiarity which has already been alluded to : its 

 bifurcation anteriorly in the lepidoptera, each spiral sucking tulie extending its branch to 

 it just behind the head. 



The esophagus is connected in the first place with the crop, an enlargement having a 

 close analogy in position and form with the crop of a bird. It is also called a stomach by 

 some writers on entomology. It is sometimes placed on a line with the esophagus, when it 

 appears as a simple enlargement of the tube ; in other instances it is placed on one side, 

 and then appears more like a sac connected with the esophagus by a short canal, and 

 serving as a kind of reservoir ; or, in other words, more analogous to the crop of birds*. 

 In certain beetles, as the Cicindela, the organ is provided with a glandular apparatus, which 

 secretes an abundant and active juice to soften and otherwise change the food deposited in 

 it. In the hemiptera it is remarkably modified in function : it loses its importance as a 

 depository of food, and becomes a part of a pumping apparatus ; whence it has been called 

 a sucking stomach. The insect in this case has the power of distending the sac, and thereby 



• It is proper in this place to notice the fact, that while there are numerous variations in the form and length of 

 the alimentary canal of insects, there are two modifications that should he particularly spoken of, namely : the 

 bot-fly has no opening at all answering to the mouth and pharynx, and hence can take no nourishment ; and in the 

 larva of the wasp and bee, the rectum is closed, and hence their economy does not require the evacuation of ex- 

 erementitious matter. 



