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

174 NATURA SOMOGYIENSIS Figure 7: Particle size distribution in protected habitat (clay) at Ropoly, plotted against the distance from the pit and the larvae stages The dendrogram in figure 8 shows the particle size distribution of the substrate caused by the sand throwing activity of the ant-lion larvae. The three typical node of cluster clearly apparent on the dendrogram correspond with the locations of the sampling (ps-the pit's side, ре-edge of the pit, pe3-3cm from the edge of the pit) irrespective of the type of the habitat (open or protected) and of the quality of the bedrock (sand, loess or clay). The analysis of the particle size preference of the larvae at different development stages was based on the comparison of the samples taken from the pit's side (ps) and from the reference point (rp) which is typical of the whole habitat. For this comparison the Ivlev's electivity index (preference index) was used. Figures 9-18 show the different substrate fraction preferences (+) and the avoidances (-) at certain larvae stages. It is clear from these figures that difference between the particle size preferences of larvae at different development stages is negligible. The minor differences in the cases of the different larvae stages are neither characteristic of the habitats (open and protected) nor of the type of substrate they are from. In open sandy habitats (Figures 9-12: TO, BO, NO, LO) the larvae prefer finer substrate fractions (0.1-0.2, 0.2-0.3, and 0.3-0.4 mm) (Ei>= +0.25). They reject the coarser substrates to a great extent (>0.5-0.8 mm Ei>= -0.35). On the sandy bedrock of Bélavár and Tótújfalu both types of habitats can be found. The difference between the particle size and the homogeneity of the substrate collected in the two types of habitats was not significant (TO-TP R=l BO-BP R=0.994 p=5.29E07). The particle size distribution is outstandingly similar in the case of the larvae of Myrmeleon bore living in open habitat (TO, BO) on sandy bedrock and in the case of Euroleon nostras of the same location (TP, BP) but of protected habitat (Figures 9-10. and 11-12.). Significant difference at these locations (TO-TP and BO-BP) could not be