Range, distribution, field identification, behaviour and exuvia description of Orthetrum ransonnetii (Odonata: Libellulidae)

Based on numerous records of Orthetrum ransonnetii from south-eastern Arabia, the Middle East, the Maghreb and the Canary Islands in recent decades, the range of this species is characterised in relation to climate and habitat parameters. The species is mostly found in hot, arid, rocky environments. Its flight period extends year-round, with an apparent bivoltine cycle at lower elevations and in the southernmost part of its range. The range of its known distribution in certain areas, particularly in the mountains of central and western Morocco, is extended. There it was met with, sometimes as permanent reproductive populations, on the northern slopes of the Moroccan High Atlas, a montane area with a heavy winter snow cover, distinct from most of its previously known Saharo-Arabian-Iranian habitats. The absence of earlier records in some regions may be attributable to both difficulties in identification and confusion with the more common and widespread O. chrysostigma and O. brunneum and also with O. brevistylum and O. taeniolatum, with which O. ransonnetii is sympatric in Central Sahara and part of Southwest Asia, respectively. Field identification criteria and the unique behaviour of the species are described. The combination of black antenodal subcostal cross-veins in dorsal view and fully hyaline hind wings is sufficient to differentiate O. ransonnetii from all other Orthetrum in the Palaearctic area. The species can be distinguished in the field from sympatric congeners, particularly O. chrysostigma, if good views or photographs are available, on the basis of several readily observable visual characteristics. The identification of the exuviae is difficult but O. ransonnetii is unique among its known West Palaearctic congeners in having more than 10 setae (instead of 3 to 8) at the base of the movable hook on each labial palp of the prementum.