ON CREEPERS. 107 



CREEPERS OF THE DUNS, OR CASED 

 CREEPERS. 



NATURE has changed her operations in perfecting the dun 

 tribes of flies. The females carry and lay their eggs or 

 spawn upon the waters the same as the browns, and like 

 them, the dun creepers are naturally cased in a thin skin to 

 protect them whilst in it ; but when the eggs of the duns 

 are hatched, each infant creeper singularly composes an 

 artificial case around it, which it increases in size and sub- 

 stance with its growth. These artificial cases are a hollow 

 cylinder of tough texture and smooth insides. The creeper 

 in its progress covers the outsides with rougher materials, 

 such as small pieces and knobs of sticks, stems, straws, 

 particles of sand, soil, etc., etc., which are fixed to the out- 

 side by an adhesive matter, peculiar to the creeper. When 

 a full grown creeper is taken out of its case, its appearance 

 is that of a dull sluggish grub, with but little animation or 

 resemblance to the bodies of their flies. Their legs are 

 short, their motions slow, and they would soon be devoured 

 by the fish had. not nature endowed them with the instinc- 

 tive power to compose an artificial covering around them 

 for shelter and protection. When in motion the head 

 and shoulders come out of the case, which sets their short 

 legs at liberty, and the case and creeper move together. 

 When the creepers are full grown they prepare for a change, 

 and ramble in search of a biding place to fix to, as we some- 

 times see the stickbait crawling at the bottom of the water, 

 often against the stream ; for it seems to be instinctive in 

 the aquatic flies to move upwards same as the fish. They 

 in general fix themselves to the under-parts of stones that 

 lie hollow in the water, and protects them from the violence 

 of the stream, where they remain in a fixed and dormant 

 state for two or three months, or until Nature has finished 

 her work and the fly is matured. The creeper then leaves 

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