126 Invertebrata. 



Locusts are terrible scourges in tropical countries, 

 devouring all vegetation and leaving bare the regions 

 over which they pass. Their body is long and 

 laterally compressed and the long hind legs act as 

 leaping organs. They produce a chirping sound by 

 rubbing the thighs against the elevated ribs of their 

 wings. In the grasshopper and cricket a similar 

 sound is produced by the rubbing together of spots on 

 the wings provided with raised ridges. 



The white ants or Termites of tropical regions 

 also belong to this order, and build ant-hills of extra- 

 ordinary size and hardness. Their colonies are very 

 complex, and consist of several kinds of inhabitants, 

 females, males, workers and soldiers. 



The dragonflies, which also belong to this order, 

 have aquatic larvae, breathing by means of tracheal 



FIG. 71. 



Larva of Dragonfly, showing the ' Mask.' 



gills or tuft-like processes of their body- wall contain- 

 ing tracheae, but with no openings. These processes 

 are lost in the perfect insect ; in one American genus, 

 however, these appendages are retained during life. 

 The larva of the common dragon-fly has a long and 

 jointed under lip, which is folded over the face when 

 at rest and is called the mask, but when the animal is 

 feeding it becomes extended as a formidable tongs- 

 like weapon for the grasping of prey (tig. 71). 



