TERENSKA NOTICA / FIELD NOTE
57
Unexpected record of the white-faced bush-cricket Decticus albifrons (Fabricius, 1775) (Orthoptera: Tettigoniidae) in Ljubljana, Central Slovenia
NEPRIČAKOVANA NAJDBA KOBILICE PRIMORSKE PLENILKE DECTICUS ALBIFRONS (FABRICIUS, 1775) (ORTHOPTERA: TETTIGONIIDAE) V LJUBLJANI, OSREDNJA SLOVENIJA
Peter TRONTELJ, Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia.
On 17th August, 2004, at about 9 p.m. I heard calls near the central Ljubljana railway station that were quite different from the usual animal sounds of this city. The calls reminded me of the nervous alarm calls of robin (Erithacus rubecula) or blackcap (Sylvia atricapilla). They were loud and piercing, heard clearly from a distance of app. 70 m despite traffic noise from the nearby road. Closer to the source of the voice, I recognized a familiar sound often heard in summer on the Adriatic coast – the calls of the white-faced bush-cricket (Decticus albifrons). Later that evening I was listening to the sound recording by Ragge & Reynolds (1998), which helped me to confirm the acoustic identification. The white-faced bush-cricket was hidden in high and partly dried ruderal vegetation, and stopped calling when I approached it to a distance of app. two meters.
The habitat chosen by the white-faced bush cricket in the centre of Ljubljana did not differ significantly from the places in the Mediterranean where usually found. It was a stony railway embankment, party overgrown with ruderal vegetation and few bushes, with adjacent gravelly parking ground, xero-thermophilous by appearance (Fig. 1). Other orthopteran species heard or observed at that place were: Tettigonia viridissima Linnaeus, Ruspolia nitidula (Scopoli), Eumodicogryllus burdigalensis (Latreille), Oedipoda caerulescens (Linnaeus), Sphingonotus caerulans (Linnaeus) and Chorthippus biguttulus (Linnaeus). During the ensuing days and weeks I revisited the place several times at different hours of the day, but did not hear or see the white-faced bush cricket again. Although this species remains active until late autumn in its Mediterranean range, the second half of the 2004 summer was probably too wet and cold in Ljubljana for this thermophilic species.
And what makes this short faunistic encounter worth publishing? Primarily the fact that in Europe this species is very rarely found in areas beyond the direct influence of the Mediterranean climate. Bellmann's (1993) mention of Nadig's record of a white-faced bush-cricket in southern Switzerland in 1924 is one of the very few data for inland Europe. According to Bellmann (1993), the northernmost populations can be found in the Durance Valley in Provence (S France). However, permanent populations
from the Slovenian coastal area (Gomboc 2003, Us 1992) reach about 200 kilometers further to the north. The geographic distance between the Slovenian coast and Ljubljana does not seem to be too great a hindrance for such a big and mobile insect. A more serious barrier pose the high, forested mountain ridges and cold, wet valleys lying in between. Moreover, given the proximity of the main railway station, an accidental transport by train from the northern Adriatic area offers a plausible explanation. Similarly, the colonization of Ljubljana by Cicada orni Linnaeus some years ago (personal observation) was probably made possible by »railway transport«, too. That colonization began in more or less the same area close to the central railway station. Nevertheless, it is less likely that the white-faced bush-cricket will establish a permanent population here like the cicadas did. It is probably premature to regard this single white-faced bush-cricket record as an indicator or consequence of the recent climatic change.
Figure 1. Calling site of a white-faced bush-cricket (Decticus albifrons) at the central Ljubljana railway station, recorded on 17th
August, 2004 (foto: Peter Trontelj).
Slika 1. Pogled na predel med Vilharjevo cesto in glavno železniško
postajo v Ljubljani, kjer se je 17.8.2004 oglašala kobilica primorska
plenilka (Decticus albifrons) (photo: Peter Trontelj).
Literature
Bellmann H. (1993): Heuschrecken beobachten, bestimmen.
Naturbuch Verlag, Augsburg. Gomboc, S. (2003): Kobilice – Orthoptera (Saltatoria). V: Sket B,
Gogala M. Kuštor, V., (ur.) Živalstvo Slovenije. Tehniška založba
Slovenije, Ljubljana. Ragge D.R., Reynolds W.J. (1998): A sound guide to the
grasshoppers and crickets of Western Europe. Harley Books and
The Natural History Museum, London. Us P.A. (1992): Favna ortopteroidnih insektov Slovenije. Clasis IV:
Historia Naturalis. Slovenska akademija znanosti in umetnosti,
Ljubljana.