A description and diagnosis is given for the female and male of Karnyothrips nevadensis sp. nov. collected in the Mojave Desert of southern Nevada. The thrips lives in small aggregations between young, tightly-clustered leaves on Yucca schidigera, a large and long-lived monocot shrub. The species is unusual for the genus by producing males that are only brachypterous and females that are only macropterous, including dealates. Co-occurrence with mites suggests the thrips is predaceous. I compare the structure of K. nevadensis with other North American Karnyothrips.