Dictyogenus fontium ( Ris, 1896 )

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 : 162-165

1.2 Dictyogenus fontium ( Ris, 1896)

http://lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org:TaxonName:952

( Figs. C.1–C .18)

Dictyopteryx fontium Ris 1896:310 (protonym)

Isogenus (Dictyogenus) fontium : Klapálek 1904:4; 1906:27; 1912:52

Isogenus fontium : Aubert 1946:64

Dictyogenus fontium : Illies 1954:215; 1955:92; 1966:358; Aubert 1959:78; Zwick 1971:358

Based on dry pinned specimens (4 males and 4 females) from different locations in the Swiss Alps, mainly the spring brooks of the rivers Reuss and Rhône (Furka Pass), as well as Rhine and Inn (Albula Pass), and one female from the Murgtal (Glarus Alps, designated as lectotype by Zwick 1971), the original description of the species D. fontium by Ris (1896) corresponds to about any Dictyogenus that is not D. alpinum . The distribution area of D. fontium , as indicated by Ris (1896), and fide Morton (based upon the collections of Eaton and McLachlan), also covers the whole of the Swiss Alps and extends into the Eastern Austrian and Southern Italian Alps (Val Anzasca, Macugnaga, Monte Rosa, Engadin between Pontresina and Samedan, Airolo, Val Viola, and even Carinthia). As a result of the revision of many Dictyogenus specimens, adults as well as nymphs, from the Austrian, Italian, Swiss and Slovenian Alps by the present author, it appears that D. fontium sensu Ris (1896) represents a species complex that can be divided into several morphospecies. Whereas adults belonging to this complex are difficult to separate, the same is not true of the corresponding nymphs, as will be shown below. For historical and nomenclatural reasons, I propose to consider the specimens of D. fontium from the spring brooks of the rivers Reuss and Rhône ( Fig. J.3 ), upon which the original description of Ris (1896) is mostly based, as topotypical.

Adults. Body length of males 15–19 mm (n = 11); females 16–23 mm (n = 12). Adult males and females of topotypical D. fontium have both macropterous and brachypterous populations, often occurring syntopically. Head mostly yellow, with brown patches ( Fig. C.1 ). M-line well visible. Interocellar yellow patch wide ( Fig. C.1 ). Pronotum brown, with a wide yellow median band extending from the anterior margin of the pronotum to its posterior margin ( Fig. C.1 ). Tawny area on each side of the pronotum, with dark, sculpted rugosities ( Fig. C.1 ). Abdominal sterna pale brown, with typical, arch-like markings (Fig. G.6). Proximal part of tibiae with a dark band. Antennae and cerci blackish to dark brown.

Male terminalia. Epiproct with very short, “dagger-like” ( Klapálek 1912) tip ( Figs. C.2 , C. 3 , C.4). Lateral stylets as wide as the epiproct stem, with asymmetrically shaped sides: proximal, inner side, convex; distal, outer side, concave ( Figs. C.2–C . 4 ). Hemitergal lobes on tergite X long and slender, leaving a wide gap between them (Fig. C.5).

Females. Subgenital plate (sternite VIII) very short, covering only the upper third of sternite IX (Fig. C.6), with or without median notch on its distal edge.

Mature nymphs. Length 13–29 mm (n = 27). Mature macropterous male and female nymphs of topotypical D. fontium are uniquely characterized by sexually dimorphic setation: whereas macropterous male nymphs have no mediodorsal setation on meso- and metanotum, the corresponding macropterous females exhibit a twin median row of erect, flexible, setae on meso- and metanotum. Nymphs of brachypterous males and brachypterous females, on the other hand, do not exhibit this kind of sexually dimorphic setation, both having mediodorsal setae on their mesoand metanotum. There are, thus, in these topotypical nymphal specimens, two instances of dimorphic setation: male macropterous nymphs differ from female macropterous nymphs, and male macropterous nymphs differ from male brachypterous nymphs. This implies, as already noted above, that male and female, as well as macropterous and brachypterous nymphs, have to be separated ahead of the identification procedure. However, in spite of this complicated situation, the patterns indicated in the matrix below prove to be very stable, and, more importantly, enable to separate with some confidence the nymphs of topotypical specimens of D. fontium from those of other regions.

No tuft of flexible mediodorsal occipital setae ( Fig. C.7 ); only stiff mediodorsal occipital setae ( Fig. C.7 ). Macropterous male and female nymphs do not have flexible mediodorsal setae on their pronotum ( Figs. C.7 , C.8). Macropterous male nymphs without flexible mediodorsal setae on meso- and metanotum (Fig. C.9); no mediodorsal flexible setae on abdominal tergites ( Fig. C.10 ); intersegmental stiff setae on abdominal tergites are very short and sparse on the first segments ( Fig. C.10 ). Macropterous female nymphs with flexible mediodorsal setae on meso- and metanotum (Figs. C.11, C.12); no mediodorsal flexible setae on abdominal tergites ( Fig. C.13 ); intersegmental stiff setae on abdominal tergites sparse and short, but regularly distributed ( Fig. C.13 ). Brachypterous male and female nymphs do not have flexible mediodorsal setae on their pronotum. Meso- and metanotum of both brachypterous male and female nymphs with flexible mediodorsal setae (Fig. C.14). No mediodorsal flexible setae on abdominal tergites (Fig. C.15); intersegmental stiff setae on abdominal tergites short and regularly distributed (Fig. C.15). Spines on paraprocts, in ventral view sparse (0–6), unevenly distributed between left and right ( Fig. C.16 ), covering at most the distal half. Cerci with short mediodorsal setae, sparsely distributed (Fig. C.17). Stipe with up to six spines, distributed in a single, basal row (Fig. C.18).

Material examined. SWITZERLAND. Canton of Valais. Zinal, Laulosses , 2400 m, 46° 07’ 43.64” N, 7° 36’ 31.63” E, 30.6.2018, 1L♁, 1L ♀, leg J.-P. G. Reding ( RED) ; Obergoms, Muttbach , 2090 m, 46° 34’ 05.4577” N, 8° 24’ 17.1582” E, 9.8.1997, 3♁, 2♀, leg. B. Lods-Crozet ( MZL, CB-13264 ) ; Bourg-Saint-Pierre, Dranse d’Entremont , 1787 m, 45° 57’ 06.51” N, 7° 11’ 53.37” E, 12.7.1943, 1♁, 1♀, leg. J. Aubert ( MZL, CB-13265 ) ; Lac du Grand Lé , torrent, 2500 m, 45° 53’ 9.312” N, 7° 08’ 35.268” E, 8.8.1942, 1♁, 1♀ b, leg. J. Aubert ( MZL, CB-13265 ) ; Lac du Grand Lé , torrent, 2500 m, 45° 53’ 9.312” N, 7° 08’ 35.268” E, 5.7.1952, 1L♁, 3L♁b, 1L ♀, 5L ♀ b, leg. J. Aubert ( MZL, CB-13264 ) ; Arolla, tributary to Borgne d’Arolla , 1968 m, 46° 01’ 26.4756” N, 7° 29’ 3.66” E, 15.7.1943, 3♁, 6♀, leg J. Aubert ( MZL CB-13265 ) ; Arolla, tributary to Borgne d’Arolla , 1968 m, 46° 01’ 26.4756” N, 7° 29’ 3.66” E, 2.9.1943, 3L♁b, leg J. Aubert ( MZL CB-13264 ) ; Imfeld, Binna , 1500 m, 46° 22’ 9.876” N, 8° 12’ 47.448” E, 13.7.1944, 1♁b, leg. J. Aubert ( MZL, CB-13264 ) ; Halse, Binna , 2060 m, 46° 22’ 34.8852” N, 8° 15’ 56.3616” E, 22.7.2004, 1♁, 1♀, leg. P. Stucki ( MZL, CB-13265 ) ; Oxefeld, Binna tributary, 2192 m, 46° 22’ 31.8216” N, 8° 17’ 09.3084” E, 19.8.2016, 5 Lb, leg. P. Stucki ( MZL, CB-16956 ; GBIFCH01210803 ) ; Oxefeld, Binna spring, 2188 m, 46° 22’ 33.7224” N, 8° 17’ 1.806” E, 18.9.2016, 2L ♀ b, leg. V. Lubini ( MZL, CB-16956 ; GBIFCH01210807 ) ; Agenetal, Aegina , 1750 m, 46° 29’ 46.9284” N, 8° 20’ 45.384” E, 25.9.1985, 1L♁b, 1L ♀ b, leg. J. Aubert ( MZL, CB-13264 ) ; 21.7.1986, 1♁, leg. J. Aubert ( MZL, CB-16956 , GBIFCH00899352 ) ; Gletschboden, Muttbach , 1800 m, 46° 34’ 12.4212” N, 8° 22’ 52.2624” E, 4.8.1997, 1♀, leg S. Knispel ( MZL CB-13264 ) ; Muttbachtal, Muttbach spring, 2500 m, 46° 33’ 32.4864” N, 8° 24’ 51.408” E, 11.9.2015, 1L ♀ b, leg. V. Lubini ( MZL, CB-16956 ; GBIFCH01210806 ) . Canton of Ticino. Val Bedretto , Ticino, 2280 m, 46° 28’ 44.22” N, 8° 24’ 7.8516” E, 25.9.1985, 1L ♀ b, leg J. Aubert ( MZL CB-13264 ) . Canton of Uri. Klausen Pass, brook Untere Balm , 1760 m, 46° 52’ 21.00” N, 8° 49’ 47.0784” E, 5.7.2004, 1L ♀, leg. H. Vicentini ( MZL, CB-13265 ) .

Distribution and ecology. Inner-alpine Swiss Rhône valley (Anniviers Valley, Binntal, Obergoms, Arolla); spring brooks of River Reuss ( Figs. J.2 , J. 3 ). High altitude torrents and springs, from 1500 m to 2500 m.

Adult flight period. June 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 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 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 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.

FIGURES C.13–C.18: nymphs of Dictyogenus fontium (topotypical). C.13—tergites of macropterous female nymph (Val d’Anniviers); C.14—mesonotum, brachypterous male nymph (Agenetal); C.15—tergites, brachypterous male nymph (Arolla); C.16—spines on paraprocts of nymph, ventral view; C.17—cerci, mediodorsal setation; C.18—spines on stipe.

FIGURES A.16–A.18: general characteristics of nymphal Dictyogenus. A.16—exuvia of nymph (D. nadigi sp. n.); A.17— abdominal tergites of mature nymph, lateral view, showing the yellow stiff and bright flexible mediodorsal setae (D. nadigi sp. n.); A.18—abdominal tergite with stiff (s), flexible (f) and clothing (c) setae (D. nadigi sp. n.).