大ボタル。

I've received a gorgeous card with a golden dragonfly and am remembering a haiku from 書道 lessons—蛍 is a firefly, vs a dragonfly, but anyway:

大ボタル oobotaru
ゆらりゆらりと yurari yurari to
通りけり toorikeri
(Issa 一茶, Hachiban Nikki / Eighth Diary, Bunsei 2, 1819—I think)

a big lightning-bug is passing by, swaying

Or maybe lurching, right, left, right, left. -keri, if I recall correctly, is continuous; a moment of fireflying along, sort of stumbling along its 通 through the air, as bugs do. 

"夏の世の闇の中を大きな蛍が悠々と光って飛んでゆく、の意。" (source, source, source; Issa chronology from the endlessly fabulous HaikuGuy, David G. Lanoue)
A big lightning-bug flies leisurely by, lighting the summer dark.