Recognising and identifying syrphids

The Syrphidae are one family of true flies, or Diptera. One of the most important distinguishing features of the Diptera is indicated in their name: di‐ptera, or two wings, referring to the fact that the adults of these insects have only one pair of membranous wings. A second distinguishing feature of many Diptera, including syrphids, is that the mouthparts are much modified, the mandibles having been lost and, in their place, there is a mop‐like structure through which these insects sop up much of their food.

 

How to tell syrphids from other flies

1.  Most exhibit one characteristic of their wings that is convenient in helping to distinguish syrphids from other flies, namely a false vein, or vena spuria, that is located towards the centre of the wing and lies more‐or‐less parallel to the wing’s long axis.

Vena-spuria

 

 

2.  A second helpful feature is the plumule, which looks like a small, downy feather, located on the side of the thorax, ventral to the wing‐base, and just anterior to the haltere. This curious little chemo‐sensory structure is not well‐studied, but is almost unique to Syrphidae.

Plumule-haltere

 

Identifying syprhids to species

Identification of syrphids to species is difficult. It requires microscope facilities and the use of scientific keys. Almost all species have to be lethally sampled to identify. The following are the identification keys recommended by Dr Martin Speight:

  • Speight, M.C.D. & Sarthou, J.-P. (2014) StN keys for the identification of adult European Syrphidae (Diptera) 2013. Syrph the Net, the database of European Syrphidae, Vol. 74, 135pp, Syrph the Net publications, Dublin. A pdf version is provided under ID guides.
  • Ball, S.G., Stubbs, A.E., McClean, I.F.G., Morris, R.K.A., Falk, S.J. & Hawkins, R.D. (2002) British Hoverflies: an illustrated identification guide, 2nd edition, 469pp. British Entomological and Natural History Society.
  • Ball, S.G., Morris, R (2013) Britain’s Hoverflies. An introduction to the hoverflies of Britain. Princeton University Press
  • Bartsch, H., Binkiewicz, E., Rådén, A. & Nasibov, E. (2009a) Blomflugor: Syrphinae. Nationalnyckeln till Sveriges flora och flora, DH53a. Artdatabanken, SLU, Uppsala. 406 pp.
  • Bartsch, H., Binkiewicz, E., Klintbjer, A., Rådén, A. & Nasibov, E. (2009b) Blomflugor: Eristalinae & Microdontinae. Nationalnyckeln till Sveriges flora och flora, DH 53b. Artdatabanken, SLU, Uppsala. 478pp.
  • Haarto, A. & Kerppola, S. (2007a) Finnish hoverflies and some species in adjacent countries. Otavan Kirjapaino Oy, Keuruu. 647pp.
  • Van Veen, M. (2004) Hoverflies of Northwest Europe: identification keys to the Syrphidae. 256pp. KNNV Publishing, Utrecht.

 

Additional resources:

  • The syrphid species accounts provide a full account, map, and photograph of each of the 180 species of hoverfly recorded from Ireland. For many species this includes information on identification.
  • Martin Speight has kindly made available a presentation from a 2012 workshop in the Data Centre. This pdf provides valuable information on finding, collecting, preserving, identifying & studying syrphids. It is 2MB in size: Getting-to-know-syrphids
  • This pdf is a simple guide to 10 Irish hoverflies that mimic bumblebees. It is provided under ID guides.
  • Steven Falk’s website has information and excellent photographs of British hoverflies.
  • Stuart Ball & Roger Morris have produced an book on Britain’s hoverflies (2013). It has lots of high quality photographs and is a fantastic resource for beginners.
  • This spreadsheet lists the syrphid species known from each county in Ireland. It is taken from: Speight, M. C. D. (2008). Database of Irish Syrphidae (Diptera). Irish Wildlife Manuals, No. 36. NPWS (database spreadsheet) Irish-hoverflies-by-county_2012 (1)
  • Diptera.info is a useful website with lots of resources, and where queries on unusual Diptera can be posted.