The nymph of a stonefly (order Plectoptera), often used as bait.
1894 Forest & Stream 43.313 MT, The trout were not taking the ﬂy to any great extent, and we found that the minnow and the helgramite or “devil scratcher” made the best bait. 1899 Amer. Angler (Ed. Harris) 29.57 MT, At present I have not been able to get you any of the “devil scratchers” as all call the helgramites here. The kind we have here are found under the stones in the stream, and in July they turn to the trout fly. . . I will be sure and send you some of those “scratchers” as soon as the weather will permit. 1923 Helena Independent (MT) 8 Feb 8/7, Sonny was fishing with “devil scratchers,” and had no thought beyond landing a whitefish. 1951 Billings Gaz. (MT) 18 Nov 20/4, Stonefly nymphs are commonly called either “scratchers” or “hellgramites,” and the caddis fly larvae are known as “rock worms.” 1953 Randolph–Wilson Down in Holler 239 Ozarks, Devil scratcher. . . Hellgrammite, larva of the dobson fly (Corydalus cornutus). [DARE Ed: The identification of the “hellgrammite” meant here is probably erroneous.] 1961 Daily Ravalli Republican (Hamilton MT) 6 June 1/2, The lunker went for a “devil scratcher,” similar to a hellgramite, on the end of an 8-pound test leader and 10-pound test line. 1977 Billings Gaz. (MT) 1 July sec D 7/4, A few days before they [=salmonflies] actually start hatching, fly fishermen will use the Montana nymph, bitch creek and wooly worm to imitate the nymph stage, also called hellgramites and, locally, scratchers. 2007 in 2020 DARE File—Internet MT, We use to call them [=hellgrammites] “Devil Scratchers”. I had always heard/thought that they were Salmon Fly larvae. When I was younger, when bait fishing was still cool on the Yellowstone River, we used them a lot for trout.