Decticus nigrescens Tarbinsky, 1930

Storozhenko, S. Yu., Sergeev, M. G. & Molodtsov, V. V., 2023, New data on distribution of Decticus nigrescens Tarbinsky, 1930 (Orthoptera: Tettigoniidae) in Russia, Far Eastern Entomologist 487, pp. 21-28 : 22-26

Decticus nigrescens Tarbinsky, 1930

Fig. 1

Decticus nigrescens Tarbinsky, 1930: 181 (holotype: male, Russia: ‘Nambovo’; kept in the Zoological Institute, St. Petersburg); Furukawa, 1948: 267; Storozhenko, 1980: 16; Sergeev, 1986: 180; 1992: 46; Otte, 1997: 299; Dubatolov & Sergeev, 1999: 47; Storozhenko, 2004: 136; Karmazina, 2010: 191; Storozhenko, 2009: 47; Liu et al., 2020: 575 ; Lapteva, 2023: 88, 100.

Decticus verrucivorus (nec Linnaeus): Pravdin & Cherniakhovsky, 1975: 362, 367.

TYPE MATERIAL EXAMINED. Russia: Jewish Autonomous Oblast, Nagibovo , 47.75°N, 131.54°E, 26.VII 1926, 1♂ (holotype), 1♀ (paratype), leg. Pljater-Plokhotzky.

OTHER MATERIAL EXAMINED. Russia: Zabaykalsky Krai: 3 km E Aleksandrovsky Zavod, 50.92°N, 117.97°E, steppe, 18.VII 1977, 5♂, 6♀ (SS); between Budiumkan and Uriyupino border post, 52.67°N, 119.95°E, 31.VII 1997, 1♀ (Dubatolov, Berezina, Kosterin ); Nerchinsky Zavod , southern vicinities, 51.29°N, 119.61°E, flood plain meadow, 09–14.VIII 1996, 6♂, 8♀ ; Amurskaya Oblast: Svobodny Trud, 51.93°N, 127.28°E, at forest edge, 12.VIII 1982, 1♂ (SS); Klimoutsy, 51.48°N, 127.64°E, at forest edge and in meadow, 10– 11.VIII 1982, 3♂, 5♀ (SS); Glukhari, 51.76°N, 128.09°E, 14–15.VIII 1982, 1♂, 1♀ (SS); 6 km E Saskal, 51.69°N, 126.95°E, meadow, 13.VIII 1982, 1♂ (SS); 40 km S Zavitinsk, Mikhailovka settlement, Zavitaya River , left side, 49.92°N, 128.83°E, 18.VII 1976, 2♂ (Moiseeva); Kulikovka, 49.79°N, 129.28°E, 21-13.VIII 2004, 1♀ (Bezborodov) ; Jewish Autonomous Oblast: Obluchye, Khingan River, left side, 48.99°N, 131.04°E, low terrace, 6.VII 1976, 1♂, 1♀ ( Moiseeva ); 6 km NE Pashkovo, 48.93°N, 130.77°E, 20.VIII 1982, 6♂ (SS); Babstovo , 48.08°N, 132.63°E, piedmont plain, sandy stone scare, very dry meadow with grasses and sagebrushes, 6.IX 1977, 1♂ (Murav'eva, Kretova, Ruban) ; Primorsky Krai: Shiryaevka, 43.97°N, 132.58°E, 17.VII 1971, 1♀ (Kuliev); Kedrovaya Pad Nature Reserve, Kedrovaya River , 43.11°N, 131.60°E, 1974, 2♀ (Cherniakhovsky); Milogradovo, 43.32°N, 134.59°E, dry clearing in forest, 13–14.VII 1982, 2♂, 2♀ (SS); 6 km SW Lyalichi, 44.02°N, 132.29°E, at forest edge and in meadow, 10-13.VII 1984, 9♂, 4♀ (SS); Dmitrievka, 44.39°N, 132.80°E, 15.VII 1988, 1♀ (Arefin); 3 km S Frolovka, 43.17°N, 133.27°E, 20–25.VII 1995, 1♂, 1♀ (SS); Barabash-Levada, 44.75°N, 131.43°E, 6.VIII 1987, 2♂ (SS); Ussuriysk, 43.82°N, 132.03°E, 20.VII 1981, 1♂ (collector unknown); Komissarovo, 44.98°N, 131.77°E, meadow, 13.VII 1980, 3♂ (SS); Lazovsky Nature Reserve , cordon Korpad, 43.29°N, 134.05°E, 25.VIII 2007, 1♀ (SS); Staraya Kamenka, 43.35°N, 134.04°E, 29.VIII 2007, 1♂, 3♀ (SS); Sikhote-Alin Nature Reserve , cordon Zimoveiny, 45.07°N, 136.62°E, 26.VII 1998, 1♀ (Kuznetsov) .

REMARKS. This species was described as “ one male (type) and one female (paratype) from Nambovo, Primorskaja Prov., collected by Mr. Pljater-Plokhotzky, 26.VII 1926 ” ( Tarbinsky, 1930). The labels of types were incorrectly interpreted by Tarbinsky; really the type material was collected from the territory of the modern Jewish Autonomous Oblast, Nagibovo settlement on the left side of the Amur River (47.75 оN, 131.54 оE) .

DISTRIBUTION. Russia (Zabaykalsky Krai, Amurskaya Oblast, Jewish Autonomous Oblast, Primorsky Krai) ( Fig. 2 ); known also from Inner Mongolia and Heilongjiang in China but records from these regions were given without exact localities ( Furukawa, 1948; Kang et al., 1990; Ma et a l., 1991).

ECOLOGICAL PREFERENCES

Stebaev et al. (1989) noted that Decticus nigrescens could be included in the ecological group mainly associated with the regions occupied by coniferous forests and forest-steppes, mainly north of the Amur River. However, all set of data on the species preferences show that it can mainly occur in quite different habitats, commonly open and relatively dry, such as some variants of the meadows and clearings in broad-leaved forests, the steppe-like vegetation on stony plots. The abundance of this species is low and varies usually around 1–2 per hour and the maximal density is about 0.01–0.02/m 2.

ECOLOGO-GEOGRAPGICAL MODEL OF DISTRIBUTION

Almost all known localities of the species are situated in either the southern parts of the Russian Far East or the easternmost areas of the Transbaikal region. The Maxent ecologo-geographic model shows that the most optimal habitats for this bush-cricket are distributed across the southern parts of the Amurskaya Oblast, almost all territory of the Jewish Autonomous Oblast, and the Primorsky Krai, except its north-eastern areas ( Fig. 3 ). However, some adjacent areas are very suitable for Decticus nigrescens as well. Among them are the southern parts of the Khabarovsky Krai, especially along the Amur River, and the north-eastern parts of Heilongjiang, NE China. Surprisingly, the north-eastern area of the Altai Mts looks like one of the most appropriate territory for the species. Certainly, finding of Decticus nigrescens in the Altai Mts is unlikely, but this area may be used for the species introduction if that will be needed in the future, e.g., for species conservation. The modest levels of suitability (about 0.4–0.5) are forecasted for wide areas of NE China, N Korea, some parts of the Stanovoy (Outer Khingan) Range and the West Sayan Mts in S Siberia. The ellipsoid model shows the similar distribution patterns ( Fig. 4 ), but its predictions look like very moderate. Perhaps these differences are determined by the limited set of variables included in the analysis.

The Maxent model performance is almost perfect (especially taking into account a few samples), because the AUC value for 25 replicates equals 0.979 ( Fig. 5 ). According the Maxent model, the precipitation of wettest month is the most important factor (contribution – 36.6%), the precipitation of warmest quarter (22.4), the annual mean temperature (11.7), and the mean temperatures of wettest quarter (10.2) are also significant. The Jackknife test allows to add the precipitation of wettest quarter as well. This means that precipitation levels of warm seasons are very essential for this bush-cricket.

Figures

Fig. 1. Decticus nigrescens female from the Lazovsky Nature Reserve, Primorsky Krai (Photo S. Storozhenko).

Fig. 2. Decticus nigrescens known localities.

Figs 3–4. Predicted probabilities of suitable conditions for Decticus nigrescens. 3 – according the Maxent model (all distribution data and bioclimatic variables for 1970–2000; point-wise mean for 25 replicates); 4 – according the ellipsoid envelope model (all distribution data and selected bioclimatic variables for 1970–2000; means for 25 replicates).

Fig. 5. Reliability test for the Decticus nigrescens Maxent distribution model (bioclimatic variables for 1970–2000; 25 replicates with cross-validation).