I stepped outside the back door at the weekend and heard a consistent humming. It could have been a distant electrical or mechanical sound but it was coming from the trees. We have sweet chestnut trees covered in ivy. The bees and flies were having a great time, almost every ivy flower had insects feeding. Contrary to common thinking ivy doesn't kill trees, it will bring down dead trees eventually but it simply climbs up the bark to seek light. It cleans the air by capturing air pollutants and provides valuable nectar for insects, especially in autumn. After the flowers come the berries that feed birds through the winter.
The commonest insects I found were drone flies (hence the droning noise!). Holly blue butterflies were also enjoying the nectar from the flowers..