The article presents the results of a study of the soil surface seasonal activity of two species of julidae, widely spread in the Balkan Peninsula: Leptoiulus trilineatus (C.L. Koch, 1847) and Megaphyllum trassylvanicum (Verhoeff, 1897). The material was collected by means of pitfall traps between May 2007 and May 2009 in natural and urban habitats exposed to varying degrees of anthropogenic pressure. In the study period 1474 specimens of L. trilineatus and 618 specimens of M. transsylvanicum were collected. The impact of the soil and air temperature and humidity on the seasonal activity of both species was measured through statistical analysis. The statistical data processing was conducted using SPSS 9.0 and StatPlus 3.5.3 software packages.
L. trilineatus and M. trassylvanicum are polytopic, mesophilic and mesotermic species with year-round activity in the studied area. There is no statistically significant correlation between the degree of anthropogenic impact and the activity of the two species.
Leptoiulus trilineatus shows equal preference for both urban and natural habitats in the studied area. The species demonstrates the typical of all millipedes bimodal activity, which is the highest in spring and the beginning of winter – in the periods from March to May and from November to December. The coefficients of correlation dependence of L. trilineatus activity on the tested abiotic environmental factors are not statistically significant. The Pearson-Brave coefficient which measures the effect of soil humidity on species activity is 0.417, which shows a positive correlation. M. trassylvanicum has the highest frequency in urban biotops such as parks in the urban and suburban areas of Shumen and in the coniferous habitats on the Shumen Plateau. In this area the species demonstrates its highest activity in spring and summer (from February to July). The abiotic factors with statistically significant effect on the soil surface activity of M. trassylvanicum are the soil and air temperature – the values of the Pearson-Brave correlation coefficients are 0.708 and 0.586 respectively.
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