Perlodes dispar ( Rambur 1842 )

Zwick, Peter, 2011, Polymorphism And Taxonomic Problems In The Perlodes Microcephalus Group (Plecoptera: Perlodidae); Perlodes Mortoni Removed From Synonymy, Illiesia 7 (26), pp. 291-296 : 292-293

Perlodes dispar ( Rambur 1842)

Material examined. Numerous specimens from Germany and the entire range between Toulouse , Sweden and Armenia were examined for egg structure. Biometry was performed on 12♂ and 7♀ from Germany, Hesse, river Fulda at Schlitz-Richthof , 10♂, 7♀ from Hungary, river Raba at Magyarlak, and single males from Rio Lozoya , central Spain; France, Pont du Gard ; Sweden, R. Njva; and Armenia, Village Kasach .

Brachypterism. Male wings are between 1.2 and 1.8 times as long as head width, the distribution peaks at a RLW of 1.4. In a RWL frequency distribution, males are widely separate from females.

Egg structure. The anchor disc margin is covered by numerous irregularly shaped polygons which are barely sclerotized and were difficult to draw ( Fig. 5 ). No individual or geographical variation was observed.

Notes. Albarda (1889) studied the types of Rambur's Perlidae in coll. Selys-Longchamps. He identified the single male from Paris as " Dictyopteryx microcephala Pictet , ♂, forma microptera" which supports the present interpretation of the name. All males in samples including P. dispar females were very dark, live specimens appearing almost black and the way in which they moved to hide reminded one of rove beetles ( Coleoptera : Staphylinidae ).

Figures

Fig 5. Perlodes spp., sclerite platelets on periphery of anchor disc of German P. microcephalus (River Fulda at Ried), P. dispar (River Fulda nr Schlitz), and Scottish P. mortoni. mo-1 to mo-7 show individual ♀♀, most from River Tweed, mo-2 from River Dee. There are 5 ♀♀ similar to mo-3 (including one from River Tay), 4 ♀♀ are similar to mo-6, 5 ♀♀ (rivers Tweed and Dee) are similar to mo-7. Orientation (centre of anchor disc is towards right hand side) and scale same for all.