Wing length 6–9 mm. Pterostigma 2-2.5 times as long as the length of the wing margin between ends of wing veins R1 and R2+3. Scutellum red or dark red. The male genitalia are figured by Doczkal and Schmid (1999).[4] Note M. mutabilis is only reliably distinguished from M. myrmicae by features of the puparium.
See references for determination.[5][6][7][8][9]
^Stubbs, Alan E. & Falk, Steven J. (1983). British Hoverflies: An Illustrated Identification Guide. British Entomological & Natural History Society. pp. 253, xvpp.
^Doczkal, D. & Schmid, U. (1999). "Revision der mitteleuropäischen Arten der Gattung Microdon Meigen (Diptera, Syrphidae)". Volucella. 4: 45-68.
^Van Veen, M. (2004) Hoverflies of Northwest Europe: Identification Keys to the Syrphidae. 256pp. KNNV Publishing, Utrecht.addendum
^Van der Goot, V. S. (1981). De zweefvliegen van Noordwest - Europa en Europees Rusland, in het bijzonder van de Benelux. KNNV, Uitgave no.32: 275pp. Amsterdam.
^Bei-Bienko, G. Y. & Steyskal, G. C. (1988). Keys to the Insects of the European Part of the USSR, Volume V: Diptera and Siphonaptera, Part I. Amerind Publishing Co., New Delhi. ISBN81-205-0080-6
^Coe, R. L. (1953). "Diptera: Syrphidae". Handbooks for the Identification of British Insects. 10 (1): 1-98. Royal Entomological Society.