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 instine- 
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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