272 



MOVEMENT 



tf- 



, J 





crawl we have not been 

 able to make out how 

 the sudden spring of the 

 hind legs is effected, but 

 they crawl much in the 

 same manner as Coleop- 

 tera, as may be seen in 

 Fig. 193, which repre- 

 sents an orthopterous 

 insect. 



Among the arachnids 

 (Fig. 194) the four feet 

 of each side alternate in 

 their movements, so 

 that there are always two 

 feet off and two feet on 

 the ground, as can be 

 seen in the case of the 

 spider. 



To distinguish the 

 feet on the ground trom 

 those which are raised 

 we illuminated an insect 

 from above, so that the 

 shadow of its legs was 

 projected on to the wKite 

 surface upon which it 

 crawled. Under these 

 circumstances the sha- 

 dow of each foot which 

 was in contact with the 

 ground extended right 

 up to the foot itself; on 

 the other hand, when 

 the foot was raised, a 

 gap existed between the 

 foot and its shadow. 



