Differences in ecomorphology and microhabitat use of four saproxylic larvae (Diptera, Syrphidae) in Scots pine stump rot holes


Correspondence: Ellen L. Rotheray, Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, U.K. E-mail: e.l.rotheray@stir.ac.uk


  1. Co-existence and microhabitat partitioning was explored in larvae of four species of hoverfly which occupy rot holes in Scots Pine Pinus sylvestris L. in Scotland, U.K. including the endangered pine hoverfly Blera fallax (Linnaeus), and three more common species, Callicera rufa (Schummel), Myathropa florea (Linnaeus), and Sphegina clunipes (Fallén) (Diptera, Syrphidae). The primary aim of the study was to investigate competitive exclusion risks to B. fallax, a species that now remains at just one site in the U.K.
  2. Morphological differences were examined between species and these were compared with microhabitat use in an artificial rot hole. In addition, larval growth was measured for three of the species in different volumes of pinewood substrate to investigate differences in development in response to varying substrate levels.
  3. Field surveys confirmed that B. fallax, C. rufa, and M. florea frequently co-occur in pine rot holes. Species differed in their growth rates and responses to variation in substrate level. Blera fallax developed quickly before winter, and decreasing substrate volume significantly inhibited growth, whereas C. rufa and M. florea took 6 months longer to achieve a critical size for eclosion.
  4. Each species inhabited a distinct depth in the rot hole and exhibited correspondingly different behaviours associated with respiration and the length of their posterior breathing tubes.
  5. The microhabitat partitioning observed in this study may facilitate the coexistence of these four species, and suggests that competitive exclusion will not hamper conservation management efforts for B. fallax.