MOTIONS OF INSECTS. 



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their mode I mean of climbing, — as it merits particular 

 attention, will occupy more time. I have already related so 

 many extraordinary facts in their history, that I promise 

 myself you will not disbelieve me if I assert that insects 

 either use ladders for this purpose, or a single rope. You 

 may often have seen the caterpillar of the common cabbage- 

 butterfly climbing up the walls of your house, and even over 

 the glass of your windows. When next you witness this last 

 circumstance, if you observe closely the square upon which 

 the animal is travelling, you will find that, like a snail, it 

 leaves a visible track behind it. Examine this with your 

 microscope, and you will see that it consists of little silken 

 threads, which it has spun in a zigzag direction, forming a 

 rope-ladder, by which it ascends a surface it could not other- 

 wise adhere to. The silk as it comes from the spinners is a 

 gummy fluid, which hardens in the air; so that it has no 

 difficulty in making it stick to the glass. Many caterpillars 

 that feed upon trees, particularly the geometers, have often 

 occasion to descend from branch to branch, and sometimes, 

 especially previously to assuming the pupa, to the ground. 

 Had they to descend by the trunk, supposing them able to 

 traverse with ease its rugged bark, what a circuitous route 

 must they take before they could accomplish their purpose ! 

 Providence, ever watchful over the welfare of the most in- 

 significant of its creatures, has gifted them with the means of 

 attaining these ends, without all this labour and loss of time. 

 From their own internal stores they can let down a rope, and 

 prolong it indefinitely, which will enable them to travel 

 where they please. Shake the branches of an oak or other 

 tree in summer, and its inhabitants of this description, 

 whether they were reposing, moving, or feeding, will im- 

 mediately cast themselves from the leaves on which they 

 were stationed ; and however sudden your attack, they are 

 nevertheless still provided for it, and will all descend by 

 means of the silken cord just alluded to, and hang suspended 

 in the air. Their name of geometer was given to a large 

 division of the caterpillars which have this power of descending 

 by silken threads, because they seem to measure the surface 

 they pass over, as they walk, with a chain. If you place 



