Pine Hoverfly dispersal

The Pine Hoverfly is one of the UK's most threatened species. It’s restricted to the Caledonian pinewoods in the Scottish Highlands, with the remnant population confined to one indigenous site. Conservation efforts to expand its population, made by a long-standing partnership of organisations, are concentrating on supplementation of its breeding habitat using cut stumps and troughs filled with wood chip to mimic pine heart-rot, plus captive breeding and translocation.  
 
A previous PhD study investigated the rates of development of larvae and different types of substrate used within the stumps/troughs (Rotheray EL et al. 2015. Ecological Entomology, DOI: 10.1111/een.12269).  

Since 2021, Pine Hoverfly larvae and adults have been released into four sites, including two sites at the RSPB’s Abernethy reserve, and the number of larvae have been monitored annually. The ultimate aim is to establish self-sustaining populations that are not dependent on these interventions and exist within natural rot-holes in mature pines. To get to this point we wish to optimise the surrogate breeding habitat we are providing and this study should help us do this.  

• Taylor HR, Rotheray E, Elliott A, MacGowan I, Sears J and Tompkins G (2021) Hovering on the edge of extinction: efforts to save the pine hoverfly. British Wildlife. 32: 547–554. 

• Taylor HR, Allott C, Tompkins G, The Pine Hoverfly Steering Group, MacGowan I (2025). A large-scale conservation breeding and translocation programme to reintroduce a Critically Endangered saproxylic hoverfly to a Scottish forest ecosystem. Insect Conservation and Diversity. https://resjournals.onlinelibrary.wiley.com/doi/10.1111/icad.70001  

The aims are to: 

1. analyse the existing long-term data set of occupied stumps and troughs, including ones colonised naturally by the reintroduced hoverflies, to assess likely dispersal distances;

2. map suitable habitat within the potential dispersal range to establish the level of connectivity between populations (eg recording presence of forage plants, mature pine trees and any natural heart rot observed);

3. test dispersal distances by setting up a trial of cut stumps at varying distances from release sites and seeing which ones are used by breeding females.  

This would involve larval surveys in September and October – if this timing doesn't work the survey data can be made available.  
 
The dispersal experiment could be carried out at the RSPB's Abernethy nature reserve and use similar methods to that for the Aspen Hoverfly, Hammerschmidtia ferruginea – see Rotheray E L et al. (2014) Journal of Insect Conservation DOI 10.1007/s10841-014-9627-7.