Charles Patterson,An Angler’s year, Londres, W. R. Russell, 1904, p. 97-98.

You are also to know that there be divers kinds of cadis or case worms that are to be found in this nation » and goes on to mention the three principal forms, winding up thus : «  These three cadises are commonly taken in the beginning of summer, and are good, indeed to take to any kind of fish, with float or otherwise. » Now we probably all know caddis, cads, or cadbait, but how few there are who properly appreciated Izaak’s words, «  any kind of fish. » Roach, dace, chub, barbel, greyling, and perch feed greedily upon them, and as our old teacher says, » doubtless they are the death of many trouts. »

As everyone is aware , they are the immature form of the flies know as sedge (natural order Phryganidae)  and closely allied groups, which live in cases composed of little sticks, stones, etc., cemented together by a gummy secretion from the insect itself.