Polyergus nigerrimus Marikovsky, 1963 is obligate parasite of Serviformica species. For the first time, this species was found on the left bank of the Enisej river near Kyzyl town (Tuva Republic) in semidesert. P. nigerrimus is a very rare species in the Baikal region of Russia, which includes Irkutsk province and Buryat republic. Over the entire period of the studies of myrmecofauna of the Baikal region, this species was recorded in only two localities on the territory of Buryat republic: in the vicinity of Kyakhta town and in the Gusinoozersk town. The ants were collected in the Olkhon district of Irkutsk province in July 2014. The method of route survey with a strip width of 2 m was used. Garmin eTrex 30 were used to register the geographical coordinates of the locations of the ants' nest. The collected ant specimens were fixed and stored in 1.5 ml Eppendorf microtubes filled with 95% ethanol. For the research the following morphometric measurements (in mm) and indices are used: HL (head length) – in full face view, the greatest length, parallel to long axis, between the distal margin of the clypeus and a line perpendicular to the most distal portion of the vertex margin; HW (head width) – in full face view, perpendicular to the long axis, the greatest width of the head, including the outer margins of the compound eyes if they protrude beyond the lateral margins of the head; SL (scape length) – the greatest measurable length of the scape, excluding the basal condyle and radicle; WL (Weber’s length) – a standardized measure of the length of the thorax (mesosoma), from the anteroventral edge of the pronotum, exclusive of the “cervical” collar (anterior flange), to the posteroventral margin of the metapleuron; SI = (SL × 100)/HW; LI = HL + WL. All measurements were made on dried and specifically mounted specimens by using a stereoscopic microscope MC-2-ZOOM. All material used in this study is stored in the entomological collection of the Core Facilities Center “Bioresource Center” at the Siberian Institute of Plant Physiology and Biochemistry SB RAS (Irkutsk, Russia). P. nigerrimus is recorded for the first time for Irkutsk Province of Russia. The specimens were collected on Olkhon Island, in low bunchgrass and fescue steppe in July 2014 (53°10’12.36”N, 107°14’0.31”E, 551 m a.s.l.). The main morphometric measurements (in mm) and indices of workers: HL 1.38-1.43, HW 1.30-1.35, SL 1.03-1.05, WL 2.08-2.12, SI 78-79, LI 3.46-3.55. Formica candida Smith, 1878 was used as a host on the Olkhon Island. The new record is the most northern in the Baikal region.

Antonov Igor Alekseevich, Candidate of Sciences (Biology), Senior Research Scientist, Siberian Institute of Plant Physiology and Biochemistry SB RAS, 132, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–45–95, e-mail: patologi@sifibr.irk.ru

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