casefly n [Attested slightly earlier in Britain (1830→); prob shortening of caseworm fly (OED3 [at caseworm] 1828→)] ?obs Cf caseworm n

A caddis fly (order Trichoptera).

1841 Harris Rept. Insects MA 18, The May-flies, or case-flies (Phry[g]aneadæ), have been separated from the Neuroptera; and constitute the order Trichoptera of Kirby. 1884 IL Bd. Fish Comms. Report 114, Among the insects [found in specimens of the common sunfish] were . . locusts and katydids . . , grasshoppers and caseflies. 1912 KY Ag. Exper. Sta. Bulletin 159.48, Adult case-flies are delicate little four-winged insects often seen at lights . . They look somewhat like a clothes moth, and are not commonly discriminated from these insects, all being called candle flies. 1926 Essig Insects N. Amer. 172 West, The adults are known as caddis flies, caddice flies, or case flies. 1934 Minneapolis Tribune (MN) 26 May 19/2, The creeper or larva of this case-fly keeps on growing until the time is ripe for the change.