Morphological variability of Cordulegaster trinacriae in Italy (Odonata: Cordulegastridae)

摘要

This paper describes the most helpful features for field identification of C. trinacriae and the relevant morphological variability encountered. In C. trinacriae the yellow frons was without a dark horizontal marking in about 70 % of the sample or showed a barely patterned frons, while the remaining 30 % showed a more or less defined dark smudge, though always narrower and less bold than in C. boltonii. The percentage of unmarked versus marked frons was similar throughout the distributional range of C. trinacriae except in Sicily, where the unmarked yellow frons was much more common (87 %) and in Campania, where individuals with a dark mark on the frons were slightly more common than unmarked ones. In C. trinacriae the occipital triangle was almost always yellow with no or almost no dark markings, cleaner, and purer yellow than in C. boltonii from central Italy. The appendages of C. trinacriae always showed the characteristic form except for a few individuals, which might be hybrids. In C. boltonii they were found to be rather variable, especially on individuals from the southern part of its distributional range in central Italy, where intermediates and hybrids occur. Here, the appendages were sometimes similar (but not identical) to C. trinacriae, and therefore, this character is considered of limited use in the field. Individuals of C. trinacriae can be distinguished in areas of sympatry from intermediate C. boltonii and from hybrids when they show the following characters: i) unmarked yellow frons; ii) bright yellow, almost unmarked occipital triangle; ii) typical deeply notched lower appendages and long, sinuous upper appendages.