TRACHEATA 



339 



damage. One species, Acridium migratorium, which is found 

 all over Europe and Asia, moves as a locust swarm, and devours 

 every green thing which it comes across. 



Fig. 190. — Acridium peregrirmm. Natural size. 



Some species attain a large size, measuring four or six 

 inches in length. 



2. Locustidae. — The Locusts are usually of a green or 

 brown colour; they have long filiform antennae, and their 

 wings lie vertically along the side of the body. The auditory 

 organ is situated upon the tibiae of the anterior pair of legs ; 

 the tarsus is four-jointed. The female bears a pair of long, 

 sabre-like processes which form the ovipositor ; this bores into 

 the ground, and the eggs are deposited by it. The stridulating 

 noise of the male is caused by drawing the rough vein of the 

 left anterior wing over a file-like structure situated on a vibrat- 

 ing membrane at the base of the right. 



