Nysius is a genus of false chinch bugs in the family Lygaeidae. At least 100 described species are placed in Nysius.

Like other seed bugs, some species in the genus have proven to be crop pests of wheat and other grains (including N. huttoni), as well as many vegetables. A unique Hawaiian radiation of the genus contains almost a quarter of the world's species (26), as well as the most diverse character set seen in the genus. In addition, two closely related species (colloquially known as wēkiu bugs) found on Mauna Loa and Mauna Kea on the island of Hawai'i, are different from the rest of Nysius by exhibiting reduced nonfunctional wings, and feed on dead and dying insects (N. wekiuicola, N. aa ).

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