The Antlion is a creature living in a big hole on the beach in Moominvalley. He is a predator and threatens to eat people who fall into his traps. The Antlion character is based upon antlion insects, which live in desert regions.
The Antlion first appears in The Moomins and the Great Flood, where he continuously throws sand at Moominmamma when she, Moomintroll, Sniff and Tullipa doesn't leave his beach.
In Finn Family Moomintroll, the same Antlion now resides in a hole on Moominvalley's beach. To try out the effects of the Hobgoblin's hat, Moomintroll and the Snork tricks the Antlion into the hat in revenge for throwing sand at Moominmamma, the hat then transform the Antlion into a hedgehog.