1 8 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



cavities for the insertion of the hindmost legs. The ventral 

 part of this segment is dovetailed into the ventral part 

 of the metathorax and appears to be a part of it. In the 

 lower angle of the dorsal part there is on each side a 

 large opening, the external opening of the auditory 

 organ. The thin membranes within these openings are 

 the tympana. The crickets and katydids have similar 

 auditory organs situated in the tibiae of the front legs. Most 

 other insects are believed to have the sense of hearing 

 situated in the antennae. The second to the eighth abdominal 

 segments are ring-like and similar. Close to the anterior mar- 

 gin of each segment just above the lateral line is a small spiracle 

 similar to the one on the mesothorax but much smaller. The 

 first abdominal spiracles are on the first segment just in front 

 of the auditory organs. The terminal segments of the abdo- 

 men are different in the male and female. The female has at 

 the tip of its abdomen two pairs of strong, curved, pointed 

 pieces which compose the ovipositor, or egg-laying organ. By 

 alternately bringing together and separating the two pairs of 

 processes that form the ovipositor and at the same time push- 

 ing the abdomen into the ground the female is able to make a 

 deep hole in which she deposits her eggs. The end of the 

 abdomen of the male is rounded and has three short incon- 

 spicuous pieces on the dorsal surface. 



INTERNAL ANATOMY 



By carefully cutting away one side of the body-wall most of 

 the internal organs will be exposed. The alimentary canal 

 occupies the greater part of the body-cavity. Its different 

 divisions, such as the short esophagus leading from the mouth to 

 the much enlarged crop which extends through the thorax to 

 the stomach, may be easily distinguished. The stomach 

 extends to about the seventh segment of the abdomen and 

 ends in the large intestine. The small intestine is a short tube 

 running from the end of the large intestine to the anal opening 

 at the end of the body. The gastric caca are a series of pouch- 

 like organs which open at the union of the crop and the stom- 



