The number of bee species appears to have declined sharply in the past 30 years, which could mean many types of bee are extinct or so rare that no one has recording a sighting
Source:
https://www.newscientist.com/article/2265680-a-quarter-of-all-known-bee-species-havent-been-seen-since-the-1990s/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home