identify hornet-like insect of greek island Samos

[Volker Knierim]

Hi,
my question may not fit exactly into this newsgroup, but there aren't too
many NGs, concerning insects,- so I apologize for annoyance.
It would be gracious, if someone could help me identify an insect, I
observed several times on Samos (Greece) this month. I couldn't take
a picture, so here is my incomplete description.

What: coloured similar to a hornet, approximately same size or even bigger.
Wings transparent, I couldn't see, if there's colour at the edges, wings
possibly shorter than abdomen. In quiet, the wings of the insect were held
like the ones of Symphyta-wasps, not folded.
When: Mid May, time of activity: midday in full sunshine.
Where: Samos, phrygana at the eastern coast.
Activity: collecting nectar or pollen from cistus specs., good and fast
flyer.
The sound while flying is similar to hornet-sound, but deeper buzzing.

If someone can help, please answer to this newsgroup or email directly to
101526.2500 at compuserve.com (Volker Knierim).
Thanx a lot.