Dictyogenus alpinum ( Pictet, 1841 )

Reding, Jean-Paul G., 2024, Notes on the genus Dictyogenus Klapálek, 1904 (Plecoptera, Perlodidae) in the Austrian, Italian, Slovenian and Swiss Alps, with the description of six new species, Zootaxa 5397 (2), pp. 151-194 : 159-162

1.1 Dictyogenus alpinum ( Pictet, 1841)

http://lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org:TaxonName:956

( Figs. B.1–B .12)

Perla (Dictyopteryx) alpina Pictet 1841:161 (protonym)

Isogenus (Dictyogenus) alpinus : Klapálek 1904:4; 1906:24; 1912:50

Isogenus alpinus : Aubert 1946:64

Dictyogenus alpinus : Illies 1954:215; 1955:93; 1966:357

Dictyogenus alpinus : Aubert 1959:77

Dictyogenus alpinum : auctt. following Steyskal 1976

Adults. Body length of males 17–21 mm (n = 33); females 18–22 mm (n = 68).Adult males and females of D. alpinum are always macropterous (Fig. B.5). Head mostly brown, with yellow patches. M-line well-marked. Interocellar area with a wide, yellow patch ( Fig. A.1 ). Pronotum dark brown, with a yellow median band extending from the anterior margin of the pronotum to its posterior margin, widened in its distal section and gradually narrowing toward the posterior margin of pronotum ( Fig. A.1 ). A tawny area on each side of the pronotum, with dark, sculpted rugosities ( Fig. A.1 ). Proximal part of tibiae with a dark band. Antennae and cerci blackish to dark brown.

Male terminalia. Male adults of D. alpinum are characterized by a long, “claw-like” ( Klapálek 1912), downcurved epiproct tip ( Fig. B.1 ). Lateral stylets narrow, tapering out smoothly towards the apex ( Figs. B.1 , B. 2 ; Zwick 1971, his Fig. 3f ). Apex of lateral stylets not wider than half the width of the epiproct stem ( Figs. B.1 , B. 2 ). Hemitergal lobes on tergite X wide and bulky, leaving only a narrow rhomboid-shaped gap between them ( Fig. B.3 ).

Females. The subgenital plate (sternite VIII) covers most of sternite IX ( Fig. B.4 ), even reaching sternite X in some specimens (Fig. B.5). By this aspect, adult females of D. alpinum are easily separable from all other species of Dictyogenus , whose subgenital plates are much shorter (Figs. C.6, D.5, D.6, E.5, E.6, F.5, F.6, G.5, H.7, I.7).

Mature nymphs. Length 13–26 mm (n = 101). Presence of a tuft of flexible mediodorsal occipital setae (Figs. B.6, B.7). This tuft of flexible setae should not be confused with the stiff, erect mediodorsal setae also present on the occiput ( Fig. B.7, G.7 , H.8). Mediodorsal setae on pro-, meso-, and metanotum long, dense, and erect (Figs. B.6, B.7). Mediodorsal flexible setae on abdominal tergites long, dense, and erect (Fig. B.12), hiding few, short, intersegmental stiff setae (Fig. B.12). Numerous spines (>20) on the paraprocts in ventral view, covering their whole surface (Fig. B.8). Mediodorsal setae on base of cerci dense and continuous, longer than the width of the cercal segment (Fig. B.9). Spines on stipe abundant, arranged in several rows ( Fig. B.10 ). Vaginal scar of mature female nymphs markedly curved (Fig. B.11). No sexually dimorphic setation is seen between male and female nymphs.

Morphological affinities. Nymphs of D. alpinum are uniquely characterized by the presence of a tuft of flexible mediodorsal occipital setae (Figs. B.6, B.7), since the nymphs of all other known species of Dictyogenus lack this feature ( Figs. C.7, E.7, G.7 , H.8). This criterion, apparently overlooked by previous authors, allows to easily separate nymphs of D. alpinum from those of all other known species of Dictyogenus .

Material examined. AUSTRIA. Obergurgl , tributary to Gurgler Ache, 1882 m, 46° 52’ 37” N, 11° 01’ 59” E, 24.9.2019, 5L, leg. W. Graf ( GRA); 1970 m, 46° 51’ 29.9592” N, 11° 0.00’ 41.3532” E, 10.11.2020, 1L, leg. W. Graf ( GRA) ; Vent , Venter Ache, 1889 m, 46° 51’ 34” N, 10° 54’ 50” E, 26.5.2004, 2♁, leg. W. Graf ( GRA) ; Matrei , Landeggbach, 2070 m, 47° 06’ 45.84” N, 12° 34’ 01.54” E, 8.7.2021, 1♁, 1♀, leg. W. Graf ( GRA) ; Ebenalm , Gössnitzbach, 1685 m, 47° 01’ 20.64” N, 12° 47’ 12.0012” E, 31.7.2017, 1♀, leg. C. Komposch ( GRA) ; Lüsenstal , Moaleralmbach, 1971 m, 47° 08’ 42.25” N, 11° 07’ 30.73” E, 6.7.2021, 2♀, leg. W. Graf ( MZL, GBIFCH00980915 , used for molecular studies) ; Bad Kleinkirchheim , Sankt Oswaldbach, 1520 m, 46° 51’ 03.33” N, 13° 46’ 02.44” E, 7.7.2015, 2♀, leg. W. Graf ( GRA) ; Bad Gastein , Gasteiner Ache, 962 m, 47° 07’ 01.33” N, 13° 08’ 10.19” E, 4.4.1998, 10L, leg. W. Graf ( GRA) ; Sankt Oswald , Sankt Oswaldbach, 1560 m, 46° 51’ 48.12” N, 13° 47’ 14.32” E, 5.8.1995, 1♀, leg. W. Graf ( GRA) ; Rossleithen , Piessling Bach, 699 m, 47° 41’ 50.352” N, 14° 16’ 28.128” E, 20.6.2022, 1♁, 25♀, leg. W. Graf ( GRA) ; Krimml , Krimmler Ache, kriab01, 1580 m, 47° 10’ 38.0244” N, 12° 10’ 58.4184” E, 7.9.2020, 1L, leg. W. Graf ( GRA) . FRANCE. Saint-Mury-Monteymond, Vorz tributary, 2000 m ,

45° 11.469921’ N, 5° 57.998372’ E, 16.6.2007, 2♀, leg. G. Vinçon ( MZL, used for molecular studies); Ristolas, Mont Viso , Malaise trap TM56, 2400 m , 44° 42’ 15.2359” N, 7° 02’ 35.3473” E, 11.7.2016, 1♁, leg. J. Claude ( RED); Malaise trap TM55, 2340 m , 44° 42’ 16.4268” N, 7° 02’ 28.5612” E, 11.7.2016, 2♀, leg. J. Claude ( RED); Isère, Saint-Christophe en Oisans , torrent du Diable, 1500 m , 44° 58’ 7.086” N, 6° 10’ 48.684” E, 2L, leg. G. Vinçon ( RED). ITALY. Piemonte. ( Cuneo ). Crissolo, Po. 1330 m , 44° 41’ 56.9976” N, 7° 09’ 27.7884” E, no date, 5♁, 5♀, 10L, leg. C. Ravizza ( MZL, GBIFCH00899326 ). Torino. Chiapili di Sopra, Carro , 1850 m , 15.10.1989, 2♀, 20L, leg. C. Ravizza ( MZL, GBIFCH00899329 ). Alto Adige, Sulden, Suldenbach , 1500 m , 10♁, 10♀, 2L, leg. C. Ravizza ( MZL, GBIFCH00899327 ); Val de Tures, torrente Riva. 1370 m , 46° 55’ 56.9976” N, 12° 01’ 29.1792” E, 19.6.1980, 5♁, 5♀, leg. C. Ravizza ( MZL, GBIFCH00899331 ). Alpi Maritime. Bagni di Vinadio, torrente Corborant. 1700 m , 44° 15’ 31.0752” N, 7° 02’ 32.0136” E, 25.7.1976, 5♁, 5♀, leg. C. Ravizza ( MZL, GBIFCH00899336 ). SLOVENIA. Kamniška, Bistrica , 600 m , 46° 19’ 33.312” N, 14° 35’ 18.9564” E, 13.05.1988, 1♁, 1E, leg. I. Sivec ( SIV); Prošček, Kneške Ravne , 680m , 46° 13’ 06.618” N, 13° 49’ 35.4324” E, 08.06.1994, 1♁, 2♀, leg. I. Sivec ( SIV); Slatenik , Bovec, 360m , 46° 19’ 05.772” N, 13° 33’ 42.2352” E, 26.05.1983, 1♁, 2♀, leg. I. Sivec ( SIV). SWITZERLAND. Canton of Vaud. Vallon de Nant, L’Avançon , 1420 m , 46° 14’ 17.3114” N, 7° 06’ 14.9856” E, 5.7.2008, 5L, leg. M. Sartori ( MZL, GBIFCH00279832 , used for molecular studies; wrongly classified under Dictyogenus fontium ). Canton of Fribourg. Charmey, Pra-Jean , Riau du Gros Mont, 920 m , 46° 35’ 41.5783” N, 7° 12’ 0.7963” E, 22.2.2007, 1L, leg. J.-P.G. Reding ( RED); L’Ardille , Riau du Gros Mont, 1110 m , 46° 33’ 56.2608” N, 7° 11’ 43.7466” E, 13.7.2010, 3L, leg. A. Reding ( MZL, used for molecular studies); Les Planeys , Riau du Gros Mont, 1030 m , 46° 34’ 10.5762” N, 7° 11’ 44.3866” E, 10.8.2010, 5L, leg. A. Reding ( RED). Canton of Berne. Hengstschlund, Hengstsense , 1219 m , 46° 42.422764’ N, 7° 23.619206’ E, 27.3.2017, 1L, leg. J.-P.G. Reding ( RED); Lengi Vorschess, Lusergraben , 1300 m , 46° 42’ 0.5619” N, 7° 23’ 42.4449” E, 13.4.2017, 3L, leg. J.-P.G. Reding ( RED); Lengi Vorschess, Lusergraben , 1300 m , 46° 42’ 0.5619” N, 7° 23’ 42.4449” E, 13.4.2017, 1L, leg. J.-P.G. Reding ( MZL, GBIFCH00280809 , used for molecular studies). Canton of Graub ̧nden, Tga, Ragn da Faller , 1921 m , 46° 30’ 37.29” N, 9° 35’ 28.24” E, 11.5.2011, 2L, leg. V. Lubini ( MZL, GBIFCH00280352 , used for molecular studies); Fafleralp, Lonza , 1770 m , 46° 26’ 02.2704” N, 7° 51’ 45.0324” E, 22.5.2008, 1f, leg. P. Stucki ( MZL, GBIFCH00279916 , used for molecular studies) .

Distribution and ecology. Widely distributed in the Alps and Prealps ( Fig. J.1 ), in large to medium-sized torrents and brooks.

Adult flight period. May to August.

Figures

FIGURES A.1–A.3: general characteristics of adult Dictyogenus. A.1—head and pronotum of adult male (D. alpinum); A.2—vesicle on sternite VII of adult male; A.3—venation of forewing of Dictyogenus (annotations by Dr. Olivier Béthoux). Photo Bertrand Launay.

FIGURES I.2–I.7: Dictyogenus vinconi sp. n. I.2—adult female, head and pronotum; I.3—epiproct and lateral stylet of adult male; I.4—ventral lobe on sternite VII of adult male; I.5—hemitergal lobes of adult male; I.6—subgenital plate of adult female; I.7—subgenital plate of adult female.

FIGURES J.3: distribution maps of Dictyogenus. J.3—distribution map of Dictyogenus (topotypical D. fontium, D. nadigi sp. n., and D. padanum sp. n.) in alpine drainage basins.

FIGURES A.4–A.9: general characteristics nymphal Dictyogenus. A.4—separation of abdominal tergites I and II; A.5— lacinia with shoulder-like angle; A.6—prefigured ventral vesicle on sternite VII in mature male nymph, ventral view; A.7— nymph, row of stiff spines on occiput (dorsal view); A.8—female nymph, sternite VIII, ventral view; A.9—female nymph, sternite VIII, ventral view.

FIGURES B.7–B.12: nymphs of Dictyogenus alpinum. B.7—mediodorsal setation of nymph (head and pronotum); B.8— spines on paraprocts of nymph, in ventral view; B.9—mediodorsal setae on cerci; B.10—spines on stipe of nymph; B.11— mature female nymph, sternite 8, ventral view; B.12—mediodorsal setation on tergites of nymph.

FIGURES A.10–A.15: general characteristics of nymphal Dictyogenus. A.10—male nymph, sternite VIII, ventral view; A.11—stiff spines and rows of flexible mediodorsal setae on metanotum; A.12—stiff spines on metanotum (D. fontium); A.13— immature nymph, tergites, dorsal view; A.14—abdominal tergites of mature female nymph, dorsal view; (ts = tergal setae; tsp = tergal spines); A.15—meso- and metanotum of brachypterous nymph.