O SINGER of Persephone!
In the dim meadows desolate
Dost thou remember Sicily?
Still through the ivy flits the bee
Where Amaryllis lies in state
O Singer of Persephone!
Simætha calls on Hecate
To “flit” means to move swiftly, in this case, through an entanglement of ivy, a  symbol for inmortality  in Greek Mythology. Like the  amaryllis [in the next line] , ivy has the property of remaining fresh and green all year round, hence why this symbol is suiting. 
 
 A bee is known to symbolize great fruits of hard labor, seeing that bees work year-round and produce sweet honey. For the bee to zoom through ivy gives one an image of eternal happiness that strongly contrasts the dark imagery of the following line. Happy notes drowned by sadder lines is consistent throughout this poem to further emphasize the surprise element of despair Wilde expresses. 
 (Interestingly, there does exist the  Ivy Bee  ( Colletes hederae ), though it wasn’t truly discovered until far after Wilde’s time.)
Theocritus