A literary caddis worm

H.G. Wells, Certain Personal Matters, The Theory of Quotation, Londres, William Heinemann, 1897, p. 133

But your vulgar author will even go out of his way to make the clothing of his thoughts thus heterogeneous. He count every stolen scrap he can work in an improvement-a literary caddis worm. Yet would he consider it improvement to put a piece of even the richest of old tapestry or gold embroidery into his new pair of breeks ?