32 ARTHROPODS 



(5) Study next the digestive system. It consists of a 

 long tube, alimentary canal, extending the entire length of 

 the body. It is usually dark green in color and occupies the 

 central portion of the body. 



With the scissors split the head down to the mouth. The 

 short tube leading back from the mouth is the esophagus, 

 Just back of it, in the region of the thorax, the tube enlarges 

 into the crop, an elongated receptacle for food. It is some- 

 times divided into two parts, ingluvies the front, and pro- 

 ventriculus the hinder portion. 



On the side of the crop imbedded in the muscles, find 

 the salivary glands, which are grapelike in appearance. They 

 secrete the saliva, and pour it into the mouth. Find the 

 ducts leading from the glands to the mouth. 



Back of this is a deep construction in which are found 

 the gastric caeca, a circle of appendages attached at the 

 sides and having both ends free. How many do you find? 

 What is their shape? The function of these glands is to 

 secrete a digestive fluid similar to the bile of other animals 

 which digests or aids in digesting the foods. 



Back of these is the stomach proper, which is followed 

 by the iltum, cylindrical in shape, but much smaller than the 

 stomach. 



Between the stomach and the ilium are great numbers 

 of small white tubes called Malpighian tubes which open into 

 into the ilium. These act as the kidneys in higher animals. 

 The colon is a small tube connecting the ilium with the 

 larger part, the rectum, which is found in the ninth and tenth 

 segments reaching the exterior of the body at the anus, or 

 vent, at the eleventh segment. 



Make a drawing of the entire digestive system (X2). 



