Parafilm

That stretchy stuff. Great fo providing that extra seal on vials, containers, etc.
A little goes a long way! Working with insects and little "critters" often means that we don't want huge amounts of anything, and massive rolls Parafilm are definitely overkill. Especially for those junior entomologists!
Parafilm will provide a seal around bug boxes to keep out unwanted intruders.
This stuff works the way we all wish plastic wrap would work. Press one end to the surface, stretch and continue wrapping to seal completely.
2 inches wide. Sold in 3 ft and 10 ft lengths.