thunderbug n chiefly WI
1 = hellgrammite n 1; hence comb thunderbug fly for the adult insect. ?obs
1870 Appleton Crescent (WI) 6 Aug 1/4, Shouldn’t wonder if Sam. Fernandez might be induced to go if it was not for the large stock of Thunderbugs he has on hand for fishing purposes! 1874 Ibid [6 June 3]/5, The commonest one [=“insect pest”] now . . is . . a sort of poor relation to the Corydalis (thunder-bugs or dam-worms) and the Dragon-flies (Devil’s darning-needles.) 1896 Youth’s Companion 70.379 nWI, Corydalus cornutus, larva, the zoölogist called him, but he was known to the small boy as “thunderbug.” . . All thunderbugs were good bait, but the very best was that thunderbug which had turned white as it advanced toward metamorphosis into a thunderbug fly. 1899 Salina Daily Republican–Jrl. (KS) [17 Aug 4]/3, A collection of bugs . . shows what is known in the far north as the “thunder-bug.” It is about as uncanny a looking creature as can be unearthed, but he used to be before the days of artificial flies a necessary appendage to the outfit of the barefoot fisher-boy of Wisconsin or Michigan. 1913 Appleton Eve. Crescent (WI) 29 Aug 1/5, What has become of the thunderbug, the former delight of the early spring bass fisherman? . . In the early spring they used to be found under stones in the water and later in the season could be found under objects on the bank. 1973 Chippewa Herald–Telegram (Chippewa Falls WI) 24 Aug sec B 3/3 (as of c1920), Thunderbugs were their [=smallmouth bass’s] favorite bait. We found them under logs, rocks and dried cow dung. Where have these tough black pinching bugs with their equally tough, leathery skin gone?
1958 Stevens Point Daily Jrl. (WI) 20 June 6/1, Conservation Warden Herb Schneider said today that the plate-size bluegills are particular though, and bite the best on hellgramites or thunderbugs. 1966 Oshkosh Daily Northwestern (WI) 4 Aug 22/2, [Advt:] Helgramites, Thunderbugs, small crabs, nitecrawlers, at Louies. 1982 Sheboygan Press (WI) 29 July 29/4, The Sheboygan Marsh is giving up some catches of perch. . . Fishermen are baiting up with thunderbugs and helgrammites. 1999 Wausau Daily Herald (WI) 20 May sec C 1/2, More anglers every year are finding a spot in their ice chests for ugly, spidery looking, hard-shelled dragon fly nymphs—commonly known as thunderbugs. 2008 in 2020 DARE File—Internet cWI, Thunderbugs are a baitshop name for dragonfly larvae, usually applied to the longer body form of the family Aeshnidae. Spider mites are a name applied to the short-bodied, long-legged larvae of the family Libellulidae. 2011 Ibid seWI, Another take on the original question [=“What do thunder bugs look like?”] would be dragon fly nymphs used for fishing bait. . . [T]he “spiders” were called thunderbugs by some old timers—we also caught the “greenies” which were long and slender, bur the spiders were by far more popular. 2020 DARE File—Internet seWI, [Advt:] Hellgrammites. . . Spider Hellgrammites AKA—Rockflies, Thunderbugs. . . Long Green Hellgrammites AKA—Dragonfly Larva.