A retaining device 1 comprises a cup-shaped trap basket 2 including a circular support edge 3. A holder 4 is disposed at the trap basket 2, includes at least two holding arms 5, 6 movable between a “holding position” and “release” position, and is a separate assembly adapted to be connected to the trap basket 2. A gear unit 8 includes a bolt 10 that is adapted to be connected with a rotatable operating element 7 and has a driving worm 9 and tooth sections 11 adapted to be engaged with the driving worm 9 and disposed at the holding arms 5, 6.