208 THYSANOUKA. LEPISMID.E. PODURIDJE. 



false legs ; and is terminated by long pointed bristles, of which 

 three are usually most remarkable. 

 The Machilis has long antennae, consist- 

 ing of a great number of joints ; its palpi 

 also are very large ; and its eyes are 

 composed of numerous facets, and occupy 

 nearly the whole head. It frequents 

 stony places, and leaps well with the aid 

 of the appendages to the tail. The 

 Lepisma, of which one species is known 

 under the name of the Sugar Louse, from 

 its aspect and habits, has the eyes very 

 small, composed of few facets, and wide 

 apart ; its body is flat, and is terminated 

 by three threads of equal length, not 

 fitted to assist in leaping. In the Po- 

 DURID^E, the appendages to the sides of 

 the abdomen are wanting ; but the ex- 

 tremity of it is prolonged into a forked 

 tail, by which these insects can execute 

 very surprising leaps. This, when not 



FIG. 533. MACHILIS. J 



in action, is bent forward beneath the 



abdomen ; and it is by the sudden extension of it, that the leap 



is produced. From this con- 

 formation, the Poduras are 

 commonly known under the 

 name of Spring-tails. The 

 scales with which their bodies 

 are covered, are objects of great 



FIG. 334.-po.niitA. interest to the Microscopist ; 



for they have a most elaborate 



and minute structure, which can only be made out by instruments 

 of the best quality ; hence they are very valuable test objects. 



