XVIII INSECTA: ORTHOPTERA 273 



less by a definite rim or overhanging flap of the thoracic 

 wall, and supplied with a nerve, nerve-ganglion, and muscles, 

 as well as with special tracheae. These " ears " are present 

 in both male and female, and are found even in many 

 species that do not produce any sound audible to the 

 human ear, though possibly grasshoppers are sensitive to 

 sounds which do not affect us. 



The term Locust is one applied popularly to any kind of 

 grasshoppers which at times multiply with great rapidity, 

 so that their offspring necessarily migrate in large numbers 

 to new pastures for food. Such locust swarms do not now 

 occur in Britain, but in some countries they are still a very 

 serious scourge, devouring as they migrate all the vegetation 

 over which they pass. 



Family 2 : Looustidab (The Long-horned Qbasshoppeks) 

 The Locustidae differ from the ordinary grasshoppers in 



Fig. 202. — Locusta vii-idissima, the Green Grasshopper. 

 (Life size.) 



having long delicate antennae and a four-jointed instead of 

 a three-jointed tarsus, also in the "chirp" being pro- 

 duced merely by rubbing together the roughened edges of 

 the wing-covers. 



The auditory organs are here placed on the fourth joint of 

 the first pair of legs, and are present in both sexes. None of 

 this family go for the long flights characteristic of the so-called 

 " locusts " of the common grasshopper tribe. 



The Green Grasshopper (Locusta viridissima) is fairly 

 common in Britain, but is rarely seen, as it is active chiefly 

 at night, when it chirps loudly, on a shrill, not unpleasant, note. 

 VOL. I T 



