EAST PALAEARCTIC SOMATOCHLORA GRAESERI SELYS OCCURS AS A POSTGLACIAL RELICT IN EUROPE WEST OF THE URALS (ANISOPTERA: CORDULIIDAE)

The East Palaearctic S. graeseri is characterized by a current disjunct distribution. New data from northern European Russia significantly modify the earlier known pattern of its distribution. The first European record west of the Urals is reported from the environs of Pinega village (Arkhangelsk province, Pinega region). The distribution range of this sp. presented here is similar to that of Coenagrion hylas and C. glaciale. Like these spp., S. graeseri is a postglacial relict in Europe and representative of a cold-stenothermal fauna that probably colonized the continent during the late Pleistocene and early Holocene. During the Atlantic period they withdrew far to the East, remaining only as isolates in the Urals and in Europe. The survival of S. graeseri in the presumptive isolate of its distribution range in the Pinega region is probably a consequence of a specific combination of severe climate and habitat/microclimatic conditions, influenced by karst. The habitat conditions of the new locality are analysed in the context of the species' requirements. The spiny exuviae of S. graeseri and details of the female abdominal pattern are presented and compared with those of Siberian and Far Eastern individuals to show the morphological variation of the sp. The diagnostic features of the exuviae, such as the large and specifically shaped lateral and dorsal spines, the thoracic banded pattern and the laterosternal sclerites on the fourth to sixth segments of the abdomen, are described.