Insect specimens can last a really long time when they are looked after. The oldest wasp specimens we looked at today were only from the 1980s, but the oldest pinned specimen in the world is a butterfly (Pontia daplidice) in the Oxford University Museum of Natural History from 1702! That means it is 313 years old!
To allow insect specimens to last this long, they have to be cared for and kept in a special way. First of all, our wasps are sorted according to their species in these little white boxes. This makes it easy to find what you are looking for!
For a great summary on the reasons entomologists need to kill some insects and have dead specimens for study, check out this post on the Ask and Entomologist blog.
Maybe the wasps that Mustard and I collect will last for 313 years too!