[Umbrian]

This morning I noticed a fluttering movement on the flowers of an oenothera and on investigating saw it was one of the hawkmoths. I knew it would be difficult to photograph as it was weighing the flower down but decided to try. When I approached it was at rest but started to flutter rather frantically as I tried to get into position. I decided to sacrifice the stem with the open flower and bend it over so that I could take my photo but it became apparent that the moth was stuck with it's proboscis deep in the flower. Gently I pulled apart the flower at its base and the moth flew away. I wonder what caused this strange phenomena.........

[JayB]

You did the right thing, apparently there is an old BBC Autumnwatch episode where Chris Packham explains how the Hawk-Moths can starve by getting stuck on flowwers.
No idea if it goes on to explain anymore about how it happens.

[JTh]

I have seen the same in  Greece with hawhmoths stuck on Oenothera speciosa. My theory is that the oenothera is a relatively new introduction to this part of the world and the local hawkmoths are not yet sufficiently  adapted to this flower, unlike moths in the New World. Just a speculation, but while I was writing these words, I made a quick search and find something that supports my thoughts, see http://www.lefourquet.net/newsletters/1006humbird.html.

[Umbrian]

Thanks Jorun - very interesting and I am glad I was able to come to the aid of this trapped one. Hope it tries different flowers from now on.