Athena Martin found the butterfly specimens, described as "priceless" by the museum, while she was working there as part of a science-related work experience project during the summer.
The butterflies had been brought back from South America by Victorian naturalist Alfred Russel Wallace.
Many of the butterflies were believed lost at sea in the 1850s. However, they had been buried away in more than 3,000 separate drawers of butterflies at the museum.
The biggest find made by Martin was a butterfly called Dismorphia, brought from the Amazon and which had remained undiscovered and unacknowledged within the museum since the end of the 19th Century, 'BBC News' reported.