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The Great Pine Hoverfly release

Returning one of the rarest species in Scotland to it's native home. By Genevieve Tompkins, Rare Invertebrates in the Cairngorms Project Officer.

Dappled sunlight falls through fragrant Scot’s pine boughs, warming the skin. Creamy sprays of rowan flowers shine brightly in the sunlight, glow ghostly in the shade. A hint of movement draws the eye. There, feeding on the rowan flowers, is the most beautiful insect. Its dark body is set off by the burst of orange on the abdomen and glint of yellow on the face. Then you spot another, beside it. You turn to a majestic Granny pine and see a third hoverfly, crawling into the damp gap where a branch came down last winter.

This image, of a diverse Scot’s pine forest filled with the glorious sight of pine hoverflies going about their business, has sustained years of hard work by countless people. And it is an image we are now one step closer to.

The Critically Endangered pine hoverfly (Blera fallax) is fast becoming the most famous insect to date. And for good reason. It holds the dubious accolade of being both very beautiful and very rare. The species is currently known only from one site in the UK, in the Cairngorms National Park. Pine hoverflies require a combination of rot holes in Scot’s pine trees (Pinus sylvestris) for larval development and a flowering understory, on which the adult flies feed on nectar. Their favoured flowers are from the rowan tree (Sorbus aucuparia).

Rowan feeding HWP (c) Genevieve TompkinsImage: Pine hoverfly feeding on rowan, Highland Wildlife Park. Credit: Genevieve Tompkins. 

Unfortunately, with changes in forestry practices and land use over the past century, diverse forests with old trees, deadwood and a rich broadleaf understory have become rare. This has not only affected the pine hoverfly, but also numerous other species which rely on complex woodlands, such as the blood-red longhorn beetle (Anastrangalia sanguinolenta), another Critically Endangered Caledonian pine forest specialist.

Work to remedy this situation began many years ago, with intense surveys for pine hoverflies and the development of a rot hole creating technique by the Malloch Society. This work was subsequently taken up by the Pine Hoverfly steering group and Rare Invertebrates in the Cairngorms project, inspiring local people to help in monitoring for the species and creating habitat. The aim is two-fold. We work with local communities and landowners on short-term management, providing artificially created rot holes. We also support land managers in their work to re-diversify forests, opening up the canopy to allow mature trees the space to develop and managing the impacts of grazing on young rowan saplings. This will provide suitable habitat for the flies in the long-term.

Genevieve Tompkins, RIC project officer and Dr Helen Taylor, RZSS field conservation programme manager_CREDIT RZSSImage: Genevieve Tompkins, RIC project officer and Dr Helen Taylor, RZSS field conservation programme manager, release pine hoverfly larva into artificially created habitat. Credit: RZSS

At the same time, a pine hoverfly conservation breeding programme was set up with the Royal Zoological Society of Scotland (RZSS), first based at Edinburgh Zoo before moving to the Highland Wildlife Park. After an initial steep learning curve, the programme has had enormous success, producing over 8000 pine hoverfly larvae in 2021.

The culmination of this work by so many different people meant that we could release our first pine hoverflies back into the wild in autumn 2021, with nearly 3000 larvae released across four sites, at RSPB Abernethy Forest and Forestry and Land Scotland Glenmore, all within the Cairngorms Connect project area. We have now returned to those sites this March, to release a further 3000 larvae, giving these new populations the best chance of survival.