112 MICROSCOPIC OBJECTS. 



and more opaque. There are also found on the same 

 wing two or three other sorts, but they are unworthy of 

 notice as proof-objects. 



" There exists in the minds of some observers a doubt 

 whether there really are any lines on this scale. Professor 

 Amici says they are strongly hygrometrical, and when 

 perfectly dry no lines are to be seen, but when moistened 

 by breathing upon them the lines appear. 



(8) " The Podura plumbea (Lea.d-colovir Springtail.) — 

 As before noticed, these insects belong to the same order 

 as the Lepisma. They are about the tenth of an inch 

 long, and leap about like fleas fPulex irritans), though 

 not so high. They are found among sawdust and damp 

 wood, abounding also in wine-ceUars ; they are very active, 

 and consequently difficult to catch. They may be taken 

 by the following method. Sprinkle a little oatmeal or 

 flour on a piece of black paper, and place it near their 

 haunts ; after leaving it a few hom-s- in the dark, the 

 paper must be carefuUy placed in a large glazed bason, 

 so that when they leap from the paper, on being brought 

 into the light, they may fall into the bason, and thus 

 separate themselves from the bait. The body and limbs 

 of these insects are covered with scales, which from their 

 extreme delicacy require great care in removing. They 

 are also very soft and easily wounded. The fluid which 

 exudes from the injury, so completely adheres to the 

 scales as to obliterate all their markings. Hence they 

 must be cautiously handled. Those who are desirous of 

 presenang these insects should keep camphor along with 



