Invertebrates on witch hazel flowers

We have a witch hazel bush halfway down the garden making a fine show with its bright yellow, sweetly scented flowers contrasting with the cold and damp.

In 1993 I wrote a note (about the same garden) for the Entomologist's Record: Nocturnal invertebrates visiting flowers of Witch Hazels, Hamamelis mollis pallida and Hamamelis japonica cultivars, in January and I have posted an edited version here:

On 20th January 1993 I walked around our garden with a torch and inspected our Wintersweet, Chimonanthus fragrans and Witch Hazel, Hamamelis mollis pallida bushes both of which were in full bloom with their sweetly scented, pale flowers.

I found nothing on the Wintersweet, but the Witch Hazel had a variety of Diptera (two-winged flies) on the flowers. There was the mosquito Culiseta annulata quite clearly feeding; two species of fruit fly (Drosophilidae), Parascaptomyza pallida and Drosophila subobscura, the latter the more common of the two; an Anthomyiid and the Common Yellow Dung-fly, Scathophaga stercoraria.  Culiseta annulata, with its distinctive white-banded legs, in one of our commonest mosquitoes and is often found in winter in outhouses or caves.  Parascaptomyza pallida is also an extremely common fly that seems to be about in most months of the year.

On 30th January 1993 I again inspected the Hamamelis mollis pallida and also two H. japonica cultivars, "Primavera" and "Arnold" after dark. The flowers were attracting numerous invertebrates including woodlice, millipedes and spiders. Insects noted were the Common Earwig, Forficula auricularia (Dermaptera: Forficulidae); an owl fly (Dipt.: Psychodidae); Sepsis fulgens (Dipt.: Sepsidae); a Pherbellia sp. (Dipt.: Sciomyzidae); Tephrochlamys rufiventris (Dipt.: Heleomyzidae); Dromius linearis (Col.: Carabidae) and a brown Noctuid moth caterpillar.

The centre part of the Witch Hazel flower seems to be constructed for insect pollination and is relatively flat and open allowing easy access to the nectaries by short-tongued species. The pollen is sticky and, in the flowers I examined closely, had been successfully transferred from anthers to styles. Most of our Witch Hazels usually set a good quantity of viable seed and it would appear that they are adapted to pollination by nocturnal invertebrates. On day-time visits I have found only Sepsis fulgens and two non-biting midges, Smittia aterrima and Limnophyes prolongatus. The last two were, I suspect, simply sheltering in the bushes rather than feeding on nectar.