Morphological separation of adult males of Piona dispersa Sokolow, 1926 and Piona variabilis (Koch, 1836) (Acari: Hydrachnidia: Pionidae)

Piona dispersa Sokolow, 1926, has long been considered as a form of Piona variabilis (Koch, 1836). However, DNA barcoding has shown that P. dispersa should be treated as a valid species. The females of both species can be morphologically distinguished but up till now, diagnostic features to separate males have not been found. Recent findings of this species in the Netherlands have provided an opportunity to study and compare males of both species. This paper presents clear and distinct characters to distinguish them. To validate the attribution of the males based on the observed morphological differences, tentative males of both species were linked to females through DNA barcoding.