D. Ceccagnoli

Larval development of Libellula depressa (Odonata, Libellulidae) from pools in central Italy

Abstract The developmental stages of the larvae of Libellula depressa were investigated for three years in permanent freshwater pools in central Italy. Eleven instars (F‐0 ‐ F‐10) of L. depressa were discriminated by size and scatter plot. Scatter plots were constructed using the following measurements: labium length, head width, metafemur length, forewing‐pad length, and total larval body length. Prolarvae instar was derived by Dyars law. The mean growth rate coefficient values were about 0.77 for isometric parameters and 0.51 for the forewing‐pad allometric parameter. L. depressa appeared to be a ‘spring species’, as defined by Corbet, and the population we studied had a mainly semivoltine life history and, probably, a small proportion of the larvae a univoltine cycle. Eggs showed direct development.

Reservoir management and its effects on the trophic organization of the macrobenthic community in a river in central Italy

The Chiascio River (central Italy) macrobenthic invertebrate community is analysed in relation to the management of a recently constructed reservoir located about halfway along the watercourse. The dam was originally planned for irrigation purposes, but since 2005 has only been used to regulate the minimum flow of the river, with partial filling in spring and total discharge in autumn. Seasonal sampling surveys, conducted from 1996 to 1999 at 13 stations along the river, yielded 45,744 specimens of benthic macroinvertebrates belonging to 109 taxa. The functional feeding analysis revealed a zone of discontinuity downstream of the dam, with high values of shredders and low values of collectors. The discontinuity is probably due to the reintroduction, in autumn, of the stored particulate organic matter. This altered the trophic structure of the benthic community just downstream of the dam, moving it towards a facies of lower stream order.

Morphometric pattern and biometry of adult Trichoptera (Italian species)

Abstract Morphometric characters of 961 adult caddisflies, belonging to 327 taxa of the Italian Trichopteran fauna were observed and measured. Sexual dimorphism is reflected in the smaller mean size of males, with mean differences in body length of 12.57%. For the order Trichoptera, regressions of the relationships among body dimensions have been used to estimate the value of exponent b and coefficient a of the allometric function y = a * xb , a power function that describes these relationships very well. The lengths (forewing, head‐wing, metafemur, and head) versus body length relationships displayed a high degree of isometry among species, with head‐wing and forewing having the highest correlation values (especially in males). The results show that most of the variance depends on isometric size variation and not on allometric shape variation among the different species. For adult caddisflies, this demonstrates constancy of the morphological model in the Italian Trichoptera.