Perga affinis Kirby, 1882
Spitfire Sawfly
 PERGIDAE,   SYMPHYTA,   HYMENOPTERA
  
Don Herbison-Evans
(donherbisonevans@yahoo.com )
and
Stella Crossley

Perga affinis
(Photo: courtesy of Alicia Johnston, taken at Serendip Wildlife sanctuary, Lara, Victoria)

These are not true Caterpillars, but are the larvae of a wasp, or more accurately a Symphytan. These larvae are gregarious they are often found in a mass of many individuals on the ground or on a tree-trunk. When disturbed, exude a nasty smelling fluid from their mouths. This latter habit has given them the common name of "Spitfires", although they do not actually spit the fluid, just dribble it. The larvae also are inclined to tap their tails in some form of communication with the group :

Perga affinis
Click for video of tail tapping, courtesy of Sandra Keil, Melbourne, Victoria,
Photo: courtesy of Viljo Bayard Guilfoil, near Hobart, Tasmania

The larvae are cylindrical and black or pale brown, with a black head and a narrow pale tail, and are covered in short white bristles.

Perga affinis
(Photo: courtesy of Gary Jamieson,
taken at Banyule Flats Parklands, Rosanna, Victoria)

The larvae are often found feeding on:

  • Gum Trees ( Eucalyptus, MYRTACEAE ).

    Perga affinis
    showing black and brown varieties nearly being stepped on
    (Photo: courtesy of Di Shanks, Blackheath, New South Wales)

    The larvae grow to a length of about 4 cms.

    Perga affinis
    male
    Drawing: William Forsell Kirby, Tenthredinidae and Siricidae,
    List of Hymenoptera, with descriptions and figures of the typical specimens in the British Museum,
    London : British Museum, Vol. 1 (1882), Plate 1, fig. 13,
    Image courtesy of Biodiversity Heritage Library, digitized by Gerstein Library, University of Toronto.

    The adult insect (it is misnamed as a 'fly') is black with a green or blue sheen, with a yellow meta-thorax, and red bands between some of the segments. The wings are transparent and pale yellow. The male wingspan is about 3.5 cms. The female wingspan is about 4.5 cms.

    Perga affinis
    female
    Drawing: William Forsell Kirby, Tenthredinidae and Siricidae,
    List of Hymenoptera, with descriptions and figures of the typical specimens in the British Museum,
    London : British Museum, Vol. 1 (1882), Plate 1, fig. 14,
    Image courtesy of Biodiversity Heritage Library, digitized by Gerstein Library, University of Toronto.

    The larvae and adults of this family are quite harmless to people. They do not sting, as their cousins the communal wasps do.

    This species is commonly found as several subspecies in

  • Queensland,
  • New South Wales,
  • Australian Capital Territory,
  • Victoria,
  • Tasmania,
  • South Australia, and
  • Western Australia.

    Sawflies are ubiquitous, with numerous species being found in :

  • Australia, and
  • the rest of the world.

    Further reading :

    Lynn E, Fletcher,
    Vibrational Signals in a gregarious sawfly larva (Perga affinis): group coordination of competitive signalling?,
    Behavioral Ecology and Sociobiology,
    Vol. 61, No. 12 (October 2007), pp. 1809-1821

    William Forsell Kirby,
    Tenthredinidae and Siricidae,
    List of Hymenoptera, with descriptions and figures of the typical specimens in the British Museum,
    London : British Museum, Vol. 1 (1882), pp. 19-20, and also Plate 1, figs. 13, 14.

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    (written 23 October 2015, updated 21 October 2022)