Population, ecology and morphology of Saga pedo (Orthoptera: Tettigoniidae) at the northern limit of its distribution

Abstract

The bush-cricket Saga pedo, one of the largest predatory insects, has a scattered distribution across 20 countries in Europe. At the northern boundary of its distribution, this species is most commonly found in Slovakia and Hungary. In Slovakia in 2003-2006, 36 known and potentially favourable localities were visited and at seven this species was recorded for the first time. This species has been found in Slovakia in xerothermic forest steppes and limestone grikes (98% of localities) and on slopes (10-45°) with south-westerly or westerly aspects (90%) at altitudes of 220-585 m a.s.l. (mean 433 m, n = 20 localities). Most individuals (66%) were found in grass-herb layers 10-30 cm high and almost 87% within 10 m of a forest edge (oak, beech and hornbeam being prevalent). The maximum density was 12 nymphs (3rd-5th instar) / 1000 m2 (July 4, 510 m a.s.l.). In a comparison of five present and previous S. pedo localities, 43 species of Orthoptera were found in the present and 37 in previous localities. The mean numbers and relative abundance of species in present S. pedo localities were also significantly higher. S. pedo individuals at the northern boundary of their distribution were expected to be smaller and lighter because of suboptimal ecological conditions there. However, the body size of S. pedo individuals from these areas were similar to the average value for the whole area. Based on analyses of present and former localities and the Orthopteran assemblages around S. pedo, the factors endangering this species, and methods for conserving it and its habitat are discussed.

Keywords

• tettigoniidae
• survival strategies
• endangered species
• large insect predators
• ecological limits