Homes for Hoverflies

Ever spotted the aspen hoverfly winging its way past you? Chances are you haven’t. These endangered insects are one of the UK’s rarest hoverflies.

Aspen hoverflies are confined to the Scottish Highlands. The main reason that these winged insects are so rare is down to the fact that they are a little picky when it comes to finding the perfect place to lay their eggs.

Edinburgh Zoo’s very own presentation keeper Ross Poulter has been working for four years to try and create the perfect habitat for aspen hoverflies to thrive in the Highlands. With only 13 hot spots for these flies to lay eggs it is a lengthy on-going project.

The hoverfly larvae need rotting wood, but not just any old tree will do; only aspen will do for these fly guys. They can detect when the sap – that gathers underneath the bark of fallen mature aspen trees – is just right for them to lay their eggs in. From the moment the aspen tree falls it takes around two years for the wood to decay and the sap to collect underneath the bark, providing the ideal conditions for larvae – even Kirsty and Phil would find this wish list a bit tricky to satisfy!

A dead aspen tree can provide a breeding ground for these hoverflies for a couple of years before it becomes too dry and then they are back on the hunt for the aspen trees, which are difficult to come by in the Scottish Highlands. Ross and the RZSS Horticultural team has been working within the Highland Wildlife Park in Inverness-shire, creating breeding habitat and protecting the small stand of aspen trees within in park so they can then be utilised as a sustainable breeding ground in the future.

Ross Poulter, presentations keeper at Edinburgh Zoo said, “This summer during the hoverflies emergence period, I’ve tried to get up to the spot in the Highlands as often as I can to carry out work and observations on the project. Aspen hoverflies are an incredibly rare species. They’re strong-hold is within Speyside in the Scottish Highlands. The key reason they are so rare is due to the lack of large stands of mature aspen trees and the conditions they need to lay eggs; it is so specific and not that easy to locate in the Highlands. Firstly, they need a fallen mature aspen tree. Secondly, the tree has to decompose for a couple of years…a little more tricky to come by. And lastly, once they do find this, the tree will only remain in this condition for a couple of years, and then it’s back to square one.”

“I would ask anyone who has mature aspen trees on their land, who might be looking to fell them or has already got a fallen one, to get in contact with me; as I would be able to put this to good use and provide these endangered hoverflies with a breeding site for a couple of years”.

Ross can be contacted on or at Edinburgh Zoo on 0131 334 9171.

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