SELF-WROUGHT AIDS TO'MOTION. 355 



is their power, in some instances, of constructing and availing 

 themselves of what may be called artificial helps. Such are the 

 aerial bridges of silken thread, and the balloons of flake, by 

 which aeronautic spiders cross a void or ascend to the clouds. 

 Such the silken ropes, descending or mounting by whose aid a 

 variety of caterpillars, especially the Loopers, are enabled to 

 break their falls from, or resume their positions upon, elevated 

 stations ; and also of this description are the rope-ladders, spun 

 of the same material and employed by the devouring crawler 

 of the cabbage to scale a garden wall, or, if we please to test 

 her ingenuity at efforts for escape, the smooth perpendicular of 

 an imprisoning glass. 



The above, and all other insect movements, are, of course, 

 to be observed at various times and seasons ; but the subject of 

 animal motion harmonizes with this present month of Novem- 

 ber, as well as with the two which have gone before it, for to 

 all three appertain strong features of external movement pre- 

 ceding arid preparatory to the external fixedness of winter. 



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