The insect book's original owner could have placed it there in the 17th century, according to Jimmy Nsubuga, Yahoo.
Rare preserved butterfly discovered in a copy of the earliest insect book published in England
A butterfly found perfectly preserved inside a Cambridge University library book may have been there for almost 400 years.
Head of Library Services at Trinity College Jenni Lecky-Thompson was shocked after discovering the insect in a specialist book from 1634.
College officials have said there is a possibility the original owner could have placed it in Theatre of Insects, which is the earliest insect book published in England...
“This one could have been put there by the first owner back in the 17th century, and if so it is amazing that is has survived there for so long.”Source: Yahoo and Trinity Hall Cambridge Channel (YouTube)