Ábrahám Levente: Válogatott tanulmányok II. - Natura Somogyiensis 9. (Kaposvár, 2006)

Ábrahám Levente: Pit building ant-lion larvae effect to the distribution of the substrate particles in their microhabitats - Tölcsérépítő hangyaleső lárvák hatása a szubsztrát szemcsék eloszlására élőhelyeiken

Natura Somogyiensis 9 167-185 Kaposvár, 2006 Pit building ant-lion larvae effect to the distribution of the substrate particles in their microhabitats ÁBRAHÁM LEVENTE Somogy County Museum, Natural History Department, H-7400 Kaposvár, P.O. Box 70, Hungary, e-mail: labraham@smmi.hu ÁBRAHÁM, L: Pit building ant-lion larvae effect to the distribution of the substrate particles in their microhabitats. Abstract: The distribution of the size of the substrate particles in and around the pits of the pit-building antlion larvae was examined at two different types of microhabitats (open and protected). Samples of substrate were taken from the side of the pits, from the edges of the pits and from 3 cm and 10 cm away from the edges of the pit. The size of the substrate particles taken 10 cm away from the edge is considered to be characteristic for the microhabitat. The samplings consisted of different quality of substrates such as sand, loess, clay and they were taken at all three larvae stages. The samples were divided into fractions by a sieve series and the distribution of the weight percentage of the granulation was analyzed. In order to compare the samples the cluster analysis and statistical tests were used. The preference calculations were performed with Ivlev's index of preference (Ei minimum -1; Ei maximum +1). In this respect the distribution of sandy area in the Carpathian Basin is in correspondence with the distribution of the pit-building ant-lion larvae living in open habitats. The preference of the ant-lion larvae living in protected habitat does not depend on the bedrock. The investigation proved that the substrate has particular spatial distribution in the pits and their environment (microhabitat). While building and repairing the pit, the larvae gather the fine particles in the pit and throw the bigger particles further out from the pit. The spatial distribution of the particle size of the substrate can be actively influenced by the chitin bristles and teeth of the mandibles and head of the larvae. Statistical analysis has proved that the particle size preference does not depend on the development stage of the larvae, it is not species dependent and it does not depend on the quality of the substrate as well. The preferred particle size of the pit-building ant-lion larvae was determined by the physical characteristics (particle size, to what extent they were cemented) of the substrate (sand, loess, clay) which is typical of the habitat. The present and the earlier studies suggest that Euroleon nostras, and very likely other pit-building species living in protected microhabitat, chose their habitats providing less food besides optimal particle size and thermal conditions. On the other hand, the species occurring in open habitats such as Myrmeleon bore, live in habitats with bigger food supply but with extreme thermal conditions and coarser particle size. Keywords: ant-lion larva, substrate preference Introduction The pit-building ant-lion larvae are sit-and-wait predators that dwell in loose soil. At the base of their pit they are sitting with open mandible motionlessly waiting for their prey (REDTENBACHER 1883, 1884, BÍRÓ 1885a, 1885b). Studying the life of the ant-lion larvae the researchers realized as early as the 18th century that these larvae live in two different types of habitats: open (unsheltered) and protected (sheltered) (WHEELER 1930). in Central Europe the species occurring in open habitats have strong correlation with the size of the sandy stretches (STEINMANN 1969, ASPÖCK et al. 1980). In open habitats