Identification criteria for exuviae of male Anax imperator and A. parthenope (Odonata: Aeshnidae)

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The accurate identification of species is critical for any biological study. Sometimes the morphological similarity between species in the same genus makes this difficult, as with the male larvae and exuviae of Anax imperator and A. parthenope, two dragonflies that often occur syntopically. This paper examines the utility of 13 numerical criteria (based on nine measurements of the mentum, anal pyramid and femur in the metathoracic legs) and one morphological criterion (shape of the margin of the epiproct expansion: straight or notched) to separate exuviae of both species. The shape of the margin of the epiproct expansion provided correct identification of 89 % of exuviae and the ratio between length and width of the epiproct expansion was the most reliable of the criteria used.