The Hemulens that live in Moominvalley are great believers in order. They like to boss other people about and expect all rules to be obeyed to the letter. The Hemulens are, however, bad at listening to other people’s opinions and completely lack a sense of humour.

Collecting has become an important hobby for many Hemulens and they don’t have time to think about much else. Once they start collecting stamps or plants, they go to great lengths to acquire the full set. And once their collections are complete, they quickly search for something new to collect.

Hemulens can be rather frightening when annoyed and even though they mean well, their stubbornness can cause a lot of trouble. Yet in spite of these general traits, they still have their own personalities. The Constable that Stinky harasses is pleasant to everyone, while the botanist is completely obsessed with collecting. They are only slightly larger than Moomins.

Hemulens appear in the first book, The Moomins and the Great Flood.