Baetis rhodani ( Pictet, 1843 )

Gattolliat, Jean-Luc & Sartori, Michel, 2008, What is Baetis rhodani (Pictet, 1843) (Insecta, Ephemeroptera, Baetidae)? Designation of a neotype and redescription of the species from its original area, Zootaxa 1957 (1), pp. 69-80 : 71-76

Baetis rhodani ( Pictet, 1843)

Material examined. Neotype. 1 male imago with corresponding larval and subimaginal exuviae, Suisse, Canton de Genève, Versoix River, Sauverny loc., 6°07’12.8”E, 46°18’41.3”N, Alt. 450m, 24.04.2006. Col. J.- L. Gattolliat, C. Chaussignand & T. Hupin.

Other material. Four male imagos with corresponding larval and subimaginal exuviae, 1 male imago with corresponding larval exuvia, 1 female imago with corresponding larval and subimaginal exuvia, 1 female subimago with corresponding larval exuvia, 2 male imagos, 2 male subimagos, 4 female imagos, 1 female subimago, 135 larvae, same data as neotype .

1 male imago with corresponding larval and subimaginal exuviae, 1 female imago and 52 larvae, Suisse, Canton de Genève, Versoix River, Richelien loc., 6°08’36.4”E, 46°16’50.2”N, Alt. 405m, 24.04.2006. Col. J.- L. Gattolliat, C. Chaussignand & T. Hupin .

Neotype and other specimens deposited in the Museum of Zoology of Lausanne ( Switzerland) except: 1 male imago with corresponding larval and subimaginal exuviae, 1 female imago and 10 larvae in the Museum d’Histoire Naturelle of Geneva ( Switzerland); 1 male imago, 1 female imago and 10 larvae in the Naturhistorische Museum in Wien ( Austria); 1 male imago with corresponding larval and subimaginal exuviae and 10 larvae in the Institute of Entomology , Academy of Science of the Czech Republic , University of South Bohemia, Ceske Budejovice ( Czech Republic); 1 male imago with corresponding larval and subimaginal exuviae and 10 larvae in State Museum of Natural History , L’viv, Ukraine .

Description.

Larva. Male larva length: body 7.1 – 8.2 mm; cerci 4.2 – 4.7 mm; median caudal filament 3.3 – 4.5 mm. Female larva length: body 7.8 – 10.7 mm; cerci 5.6 – 6.6 mm; median caudal filament 4.5 – 5.6 mm.

Colouration. Head (Fig. 21) medium brown, Antennae yellowish brown, darker proximally. Prothorax medium brown with yellowish pattern; mesothorax medium brown with yellowish longitudinal stripes; metathorax medium brown. Legs: femora medium brown with a proximal and distal yellow mark, tibiae yellowish except medium brown ahead tibio-patellar suture and at apex, tarsi yellowish except proximally medium brown. Terga (Fig. 22) yellowish brown to medium brown with generally two symmetrical dark brown spots; terga II, III, VII and VIII darker. Sterna I to V yellow to light brown without pattern; sterna VI to IX medium brown to dark with two or four central ecru spots. Cerci ecru without annulations or stripes.

Head. Antenna ( Fig. 10 ): scape with small scales and a patch of small and very thin setae. Pedicel with elongated apically rounded scales more abundant near distal margin.

Labrum ( Fig. 1 ) rounded with the distal margin somewhat straight, width/length ratio 1.55–1.65; dorsal face of labrum ( Figs. 1 ; 7 – 9 ) with an arc subparallel to distal margin formed by 1 + 8 to 10 long and stout setae, more or less arranged in 1 or 2 rows, 3 to 5 finer setae laterally, short and fin setae scattered proximally; ventral surface with about 6 short pointed setae disto-laterally; distal margins bordered with long and feathered setae.

Hypopharynx ( Fig. 2 ) with a trilobed lingua with a broad central lobe, covered apically with minute setae, lingua with a dark H-shaped mark; superlingua as long as as the lingua.

Right mandible ( Fig. 3 ) with 7 incisors; row of thin setae on outer margin of outer of incisors absent; prostheca elongated and slender; no setae between prostheca and mola; proximal half of mandible with abundant thin setae.

Left mandible ( Fig. 4 ) with 6 incisors; prostheca with 6 similar denticles and an elongated comb-shaped structure; no setae between prostheca and mola; proximal half of mandible with abundant thin setae.

Maxillae ( Fig. 6 ) with 4 short teeth, none of them opposed to others; apico-laterally with one row of medium setae; 2 spine-like dentisetae and 8 to 12 long setae; palp 2-segmented longer than galea-lacinia, segment I 0.8 x length of segment II, tip of segment II ( Fig. 11 ) with a nipple and a single stout scale apically, segments I and II almost bare except apex of segment II.

Labium ( Fig. 5 ) with glossae clearly shorter than paraglossae; glossae triangular with broad base, inner margin and distal half of outer margin with medium setae, a few scattered setae on ventral face, no setae on dorsal face; paraglossae with three rows of long and curved setae apically, ventral face with 1 transversal row of about 7 medium setae, dorsal face with 2 long and thin setae apically; labial palp 3-segmented; segment I slightly shorter than segment II and III combined; segment II conspicuously expanded apico-laterally, with an oblique row of 5 medium setae; segment III ogival, inner margin noticeably more convex than the outer; segment III with scattered stout setae.

Thorax. Forelegs ( Fig. 19 ). Dorsal margin of femora with medium blunt setae; abundant proximally and scarce apically; short and stout setae roughly arranged in 2 rows subparallel to dorsal margin; dorsoapical setal patch formed by several short setae; ventrally with abundant short and stout setae; upper face with abundant scales and scale bases.

Tibiae with a row of very tiny setae and a row of short and very thin setae dorsally; ventrally and laterally with tiny setae, more robust setae apico-ventrally; tibio-patellar suture present.

Tarsi dorsally with a few short and very thin setae and a few very tiny setae; ventrally with a row of short and pointed setae and a few additional short and pointed setae; lateral faces with thin and short setae; tarsal claws (Fig. 20) hooked, with 1 row of 12 to 14 acute teeth increasing in length toward the apex; subapical setae absent.

Abdomen. Terga ( Figs. 12–14 ) with spatulate setae (spatulas sensu Godunko et al. 2004b), thin and long setae and scale bases, triangular broad scales rare and only present near proximal margin; posterior margin of all terga with a row of spatulate setae parallel to the distal margin; triangular spines absent on terga I to III, very rare on tergum IV ( Fig. 12 ), present on terga V and VI ( Figs. 13–14 ), abundant on terga VII to IX. Sterna ( Fig. 15 ) with scales, scale bases, spatulate setae and very thin setae scattered on surface; distal margin smooth without spatulate setae and spines.

Gills ( Fig. 16 ) on segments I to VII slightly asymmetrical; tracheation reduced but marked; stout spines and patch of very thin setae along dorsal margin ( Fig. 17 ); ventral margin bordered with brown colouration.

Paraproct ( Fig. 18 ) with thin setae and a few scale bases, spatulate setae mainly present near distal margin; margin with 15 to 25 spines; postero-lateral extension with a few thin setae and without scale bases, margin with short spines.

Cerci with patch of thin setae on inner margins; median caudal filament similar to cerci except patch of more abundant setae present on both sides.

Male imago. Length: body 8.1 – 8.9 mm; forewing 8.0 – 8.4 mm; hindwing 1.7 – 2.1 mm; cerci 16.5 – 18.0 mm, length of foreleg: femur 1.30 – 1.65 mm; tibia 2.00 – 2.30 mm; tarsi T1 0.85–1.10 mm; T2 0.65 – 0.85 mm; T3 0.40 – 0.50 mm; T4 0.20 – 0.25 mm.

Colouration. Head medium brown to dark brown; scape and pedicel medium brown, darker proximally, flagellum ecru. Facetted surface of compound eyes orange, lateral face darker with a brown ring at base. Thorax medium to dark brown. Legs ecru except forelegs ventral and partially dorsal margins of femora, apex of tibiae medium brown. Wings hyaline with dark brown venations. Abdomen: tergum I medium brown; terga II to VI ecru with a symmetrical coma shaped medium brown mark and medium brown laterally and apically; terga VII to IX medium brown with dark stripes. Sterna uniformly ecru except sternum I medium brown and sterna VII to IX with longitudinal medium brown stripes. Cerci and median caudal filament ecru except proximal segments with dark brown joints. Genitalia yellow except base of the basal segment dark brown.

Forewing ( Fig. 23 ). Pterostigma with about 10 cross-veins, most of them not reaching the radial vein, horizontal veinlets joining different cross-veins; double intercalary veins shorter than distance between corresponding main veins in proximal part of wing and longer than distance between corresponding main veins in distal part of wing

Hindwing ( Fig. 24 ) with an erected costal spur at ¼ of the length of wing; three longitudinal veins reaching margin, incomplete veinlets between main longitudinal veins.

Genitalia ( Fig. 25 ): basal segment of forceps longer than broad; segment I and II almost fused; segment I with a rounded inner projection apically; segment II with parallel margins; segment III rounded as long as broad.

Female imago. Length: body 7.1 – 8.7 mm; forewing 8.3 – 9.1 mm; hindwing 1.8 – 2.1 mm; cerci 12.0 – 14.0 mm.

Colouration. Head and thorax medium to dark brown. Legs ecru. Terga uniformly dark brown, Sterna ecru except sterna VII to IX medium brown.

Male and female subimagos. Similar to imagos except pattern faded.

Figures 21– 22. Larval structures of Baetis rhodani : 21: head and thorax. 22: abdomen.

Figures

FIGURES 7–11. Larval structures of Baetis rhodani: 7 – 9: labrum of different specimens. 10: detail of antenna (scape and pedicel). 11: tip of maxillary palp.

FIGURES 1–6. Larval structures of Baetis rhodani: 1: labrum (left: ventral; right: dorsal). 2: hypopharynx. 3: right mandible. 4: left mandible. 5: left maxilla. 6: labium.

FIGURES 12–19. Larval structures of Baetis rhodani: 12: distal margin of abdominal tergum IV. 13: distal margin of abdominal tergum V. 14: distal margin of abdominal tergum VI. 15: distal margin of abdominal sternum IV. 16: gill IV. 17: dorsal margin of gill IV. 18: paraproct. 19: foreleg. 20: tarsal claw.

FIGURES 23–25. Male imaginal structures of Baetis rhodani: 23: forewing. 24: hindwing. 25: genitalia.