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The flower
bee that I have described in an earlier Nature
Note is a bee that can be mistaken for a hoverfly. The
bee-fly that visits the same flowers is a fly that can
be mistaken for a bee. In other words, I have to look
carefully to see which is which. Both have the brown,
furry body of a bumblebee and the whining, darting
flight of a hoverfly.
The bee-fly is distinguished by
the long, needle-like proboscis that looks as if it
could inflict some damage to tender skin. But it is
the mouthpart of a nectar-sipper rather than a
bloodsucker. When
feeding, it appears to be hovering in front of the
flower but is, in fact, holding the petals with its
long front legs.
So the adult bee-fly is quite a
charming visitor to the flower borders. It is the
larvae that have less than pleasant habits.
They are parasites of the grubs
of solitary bees. The female bee-fly scatters her eggs
as she flies. They fall to the ground, where they
hatch into minute, wormlike larvae. These penetrate
the nests of the bees and feed on their grubs by
sucking them dry.
Eventually they are faced with
the problem of getting out of the nest. Young bees use
their powerful jaws to bite their way out. The
bee-fly's mouthparts are totally unsuitable for this
but it has developed a remarkable structure for the
task. The head of the pupa is set with a coronet of
strong spines which is used to batter a way out. The
pupa case then splits open and the adult bee-fly
emerges and flies away.
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