Frequent US port of entry quarantine interceptions of unidentifiable larval Leucothrips (Thysanoptera: Thripidae) species in association with Codiaeum variegatum (L.) Rumph. ex A. Juss. (Euphorbiaceae) ornamental plants from Costa Rica, initiated research to determine if these thrips were an invasive threat to US agriculture. Larval and adult Leucothrips were collected from the new growth leaves of C. variegatum and other plants in Florida and Costa Rica. There were no morphological differences among adult specimens from different hosts in Florida and Costa Rica; all identified as Leucothrips furcatus Hood by comparison with type specimens. However, morphological differences in larvae associated with these adult specimens were evident. DNA sequences of the mitochondrial cytochrome oxidase c subunit 1 gene (COI), and 2 regions of the nuclear ribosomal cistron (rRNA; the complete internal transcribed spacer 2 [ITS2], and a section of the 28S large subunit rRNA) were used to verify that larvae and adults collected at the same site were the same species. Molecular data revealed species level divergence congruent with larval morphological differences.