Perla carantana-a new species of the genus Perla (Plecoptera: Perlidae) from Austria and Slovenia

Members of the genus Perla are the largest, and amongst the most endangered European stonefly species. During a revisionary study of this genus, a new species was discovered at several localities in Austria and Slovenia; Perla carantana was named after Carantania, a 7 11 century political unit within the territories of Austria and Slovenia. Adults and larvae are nearly indistinguishable from the sympatric species, Perla burmeisteriana Claassen, but the two species can be clearly distinguished on the basis of egg chorion morphology.


Introduction
Members of the genus Perla are the largest European stoneflies and the genus name is the oldest still in use for a group of stonefly species. In the Illies catalogue (1966) nearly 300 species were assigned to the genus, but Sivec et al. (1988) reduced this number to only eight species found from Britain and Ireland, through the circum-Mediterranean region of Europe and North Africa to the Caucasus and Iran. Taxonomy of the genus has never been studied in detail, but four species names proposed more than a century ago have been applied, with varying accuracy, to the complex of species found in Central Europe.
The present investigation grew out of an attempt to identify new material collected in the Balkans and Turkey and an effort to construct a reliable larval key for the genus. Earlier results (Sivec & Stark 2002) support recognition of a minimum of 12 Perla species, including two that had previously been undescribed, and suggest that the only consistently reliable character for species recognition in the genus is egg chorionic detail.
Surprisingly, several specimens were found among recently collected or older museum material from Austria and Slovenia, completely within the range of P. burmeisteriana, which have a distinct egg and are therefore recognized as a new species.
Specimens used in this study were made available from the following museums and other
Occipital area of head, callosities and M-line pale, rest of head dark brown (Fig. 4). Femora and tarsi dark brown, tibiae paler except proximal and distal parts. Antennae uniformly brown, palpi paler, cerci dark brown.
Male genitalia: Abdominal segment 9 and 10 of the typical Perla type (Figs. 1-3). Hemiterga similar in shape to those of P. burmeisteriana, not as simple and straight as those of P. pallida, and not so strongly curved as those of P. marginata. Penis Orifices of micropyles with thin raised rims.
For detail comparison of egg structures with other species see in Sivec & Stark (2002).

Etymology
The species name is based on the historical-territorial unit of the 7 th -11 th centuries in the area of present day Carinthia in Austria and Slovenia, and is used as a noun in apposition.

Comments
A closely related species, P. burmeisteriana, is widely distributed in Europe and also recorded in North Africa. In Europe P. burmeisteriana is reported from the general area bounded by Spain, Netherlands and Luxemburg to the Carpathian Mountains, Macedonia and Montenegro. The type locality is in Germany and there is a clinal variation in egg morphology toward the southeast. Reports of this species further to the east are suspect because a different species in the complex, P. zwicki (Sivec & Stark 2002) is reported from Turkey.
Perla carantana is known from several localities in Austria and Slovenia within the general distribution range of P. burmeisteriana, but that species, now nearly extinct, inhabits larger larger sreams and rivers and the new species occurs in smaller streams.