That's an entomologist.
An entomologist is a person who studies insects.
a person who studies and collects mollusc shells as a profession or hobby paula
Numismatist
There does not appear to be a name for it.
Weird
Quodophile.
Phonographer.
What is the name of a person that studies organisms
Someone who collects everything would be called a hoarder - this type of person may have OCD as well.
Some of the names given for a person who collects trains:model train collectormodel train enthusiasttrain modeler
Gun-collector
usher