208 



HIGH KCHOOIi ZOOLOGY. 



Locusts ai-e capable of produciag sounds by rubbing the hind 

 legs against the wing-covers, and they have also organs fitted 

 for jjerceiving sounds. These are situated on the first abdominal 

 segment, and consist of a vesicular 

 auditory sac, suspended on a stretch- 

 ed tympanic membrane. 



24. Fig. 141 indicates the chief 

 parts of the intestinal system. The 

 oesophagus, on ascending from the 

 mouth-cavity (into which salivary 

 glands ojien), dilates into a crop, the 

 lininc: of which is furnished with 

 hairs regularly arranged. At the 

 junction of the crop with the stomach 

 ai'e several coeca, which serve to in- 

 crease the intestinal surface, while at 

 the junction of the stomach with the 

 intestine pi'oper, the Mal[)higian or 

 urinary tubes are situated. The 

 heart is an elongated vessel occupy- 

 ing the first seven abdominal seg- 

 ments, and the respiratory organs 

 are a comi)licated system of air-tubes, 

 opening by ten pairs of ai)ertures 

 (stigmata or spii'acles) to the outside. 

 Two of these are thoracic, being situ- 

 ated in front of and behind the meso- 

 thorax, while the other eight are on 

 the anterior eight abdominal seg- 

 ments. The spiracles comnmnicate 

 directly with two longitudinal lateral 

 air-tubes ; these give off the smaller 

 tracheae to the tissues, but the spir 



