Like the ancient Scottish trees on which its larvae feed, the pine hoverfly is suffering.

Numbers have plummeted as modern forestry practices deprive it of the gnarled old “granny pines” where its young grow.

Though the fly is tiny and has nothing of the star power of the golden eagle, beaver or wildcat, it is just as crucial to the sustainability of Scotland’s iconic landscapes, acting as a vital pollinator for species such as the rowan tree.

Today the strikingly coloured insect is on the verge of extinction and has not been seen in the wild in its adult form for over seven years.

The fly’s last remaining UK refuge is believed to be in the Cairngorms National Park, where experts at the Royal Zoological Society of Scotland (RZSS) have launched a major conservation effort to boost its population.

But the coronavirus lockdown threatens to torpedo their achievements.

Visitor attractions such as Edinburgh Zoo remain shut in a bid to bring the outbreak under control, meaning a vital source of revenue has been cut off.

Now RZSS staff are fighting back with a dedicated video series aimed at promoting their work to protect the hoverfly and other vulnerable international species such as the rockhopper penguin and giant armadillo.

They hope the videos will leave viewers better informed about the plight of critically endangered animals - and prompt them to chip in with much needed donations.

Dr Helen Taylor, RZSS Conservation Programme manager, said: “Because of the lockdown, we do not have the income from zoo visitors we would normally have to support our wider conservation work.

“We want to inform and entertain but we’re also looking for help with donations to fund this.”

The videos come as efforts continue to stabilise the world’s rockhopper penguin populations, which have been hit by major crashes in places such as the Falklands.

The giant armadillo has been listed as endangered since 1976.

Both species are likely to draw the lion’s share of public interest in the RZSS video series.

However, Dr Taylor stressed that the pine hoverfly was an essential addition.

“It’s not a big, fluffy, charismatic animal but it’s just as important – and if we want to reintroduce the big, fluffy animals back into the environment then we need to protect these smaller animals that have a really key function, otherwise there won’t be an environment for the bigger animals to come back to,” she said.

“We are very concerned about the future of the pine hoverfly and not just in Scotland – because, in the UK, it’s only found in the Cairngorms.

“The Cairngorms National Park is the last refuge for the pine hoverfly that we know of within the UK. This is conservation on a knife-edge.”

The fly is a delicate species with highly specific requirements and falling numbers reflect the decline of the ancient Caledonian pinewoods where it once thrived.

In the wild, its larvae live within the rotting parts of older trees, feasting on the bacteria that collect there.

But the tendency of modern forestry to fell pines before they reach the age at which these “rot holes” usually form has had a damaging impact on the fly’s natural habitat and its population.

Now Dr Taylor and her colleagues have launched a captive breeding project at RZSS Highland Wildlife Park to turn the situation around.

They work in a small wooden shed, carefully growing the hoverfly larvae in jam jars and mixing pine wood with rain water to replicate the rot hole environment.

The larvae are then transferred to hummus pots when they turn into pupae.

Dr Taylor said the project presented a number of challenges, not least because of the fly’s rarity.

“We don’t tend to put a number on how many are left,” she added.

“They are just really hard to find. At the moment we have only found them in this one location [in the Cairngorms National Park]. This is a species on the verge of extinction in the UK.

“The pine hoverfly is a very important pollinator for tree species such as the rowan tree. They break down waste when they are in their larval stage – substances such as dead wood and so on.

“And, when they are present in high enough numbers, they provide food for other animals in the eco-system. When we lose a species like this it’s very serious.”

Fears over the future of Scotland’s pine hoverfly come as insect populations across the world plummet.

In February, a major UN summit was told that about half of all species are rapidly declining while a third face extinction, including those which were once common and widespread.

Country representatives attending the Conference of the Parties to the Convention on Migratory Species (CMS), which took place in Gandhinagar, India, also considered research which estimates that, at the current rate, 40 per cent of the world’s insect species could become extinct over the next few decades.

A range of factors are thought to be behind plunging numbers. These include habitat change and loss, the polluting effect of pesticides and fertilisers, invasive species, pathogens and climate change.

Dr Taylor said the trend was a real cause for alarm and made the conservation work being carried out by RZSS staff all the more important.

“We are seeing drastic declines in insect populations all over the world at the moment,” she added.

“The rates [of decline] are really quite scary. Every pollinator we lose is going to have an impact. This is a last-ditch attempt for the pine hoverfly.”

Meanwhile, important work is taking place to create another stronghold for the species in Strathspey. Kenny Kortland, Wildlife Ecologist with Forestry and Land Scotland, said: “As a member of the Scottish Hoverfly Group, we support efforts to conserve this beautiful fly in various ways and applaud all efforts to increase its presence.

“It is a long-held ambition of ours to have populations of pine hoverfly restored to our woods.

“Species such as this can only exist where there is a sufficient quantity and quality of deadwood... so we have been leaving increasing amounts of this invaluable habitat. The re-establishment of pine hoverflies would indicate that our deadwood policy is working... and that would be the perfect reward.” 

You can access and view the RZSS video series here.