ON CREEPERS. 109 



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 while 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 substance with its growth. 

 These artificial cases are a hollow cylinder of tough 

 texture and smooth insiders. The creeper in its pro- 

 gress 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 

 outside 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 fishes had not na- 

 ture endowed them with the instinctive power to com- 

 pose an artificial covering around them for lodgment 

 and protection. When in motion the head and shoul- 

 ders 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 sometimes 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 up- 

 wards same as the fish. They in general fix themselves 

 to the under-parts of stones that lie hollow in the wa- 

 ter, and protects them from the violence of the 

 stream, where they remain in a fixed and dormant 



