The lac insect genus Tachardiella Cockerell is reviewed and 17 species are recognized, including one new species. The adult female of Tachardiella palobrea Kondo & Gullan sp. n. is described and illustrated based on material collected in Argentina on 'brea', Parkinsonia praecox (Fabaceae). The adult female of Tachardiella argentina (Dominguez) is redescribed and a lectotype is designated based on newly discovered syntype material in the Bohart Museum of Entomology, University of California, Davis (BME). Diagnoses and notes are provided for the other species of Tachardiella studied and a lectotype is designated for Tachardiella ferrisi Chamberlin. A taxonomic key to separate all known species of lac insects in the New World is provided.