It is well known that the same organism may be known by different common names in different areas (e.g. "cougar", "panther", "puma", and "mountain lion") and that the same common name may be used for different organisms in different areas (e.g. "blackberry"), but the assumption is that (pseudo-)Latin scientific names like Achillea millefolium "yarrow" are unique. Recent work by Kew Gardens and the Missouri Botanical Garden, with numerous collaborators, has revealed that this is not quite true: of 1.04 million species-level names, they classified only about 300,00 (29%) as accepted names. They classified 480,000 names (46%) as synonyms for accepted names and 260,000 (25%) as unresolved, meaning that the available data is not sufficient to determine whether or not they designate distinct species. By way of example, a query for Achillea millefolium reveals that it has synonyms such as Achillea ambigua, Achillea angustissima, Achillea borealis, and even some in other genera, such as Chamaemelum tanacetifolium. You can look things up yourself at The Plant List.
No word yet on beetles.