Arthropleidae BALTHASAR, 1937

Monotypic, represented by 2 species in Europe and Imagines with wings similar to the heptageniid type,

North America. The family Arthropleidae is currently in fore wing vein RSa2 not directly connected with defined as monophyletic by the following apomor- RSa (Kluge 2004, Phyl. Syst. Eph., p. 116, fig. 53 phies: in larvae mouthparts are highly specialized, e.g. C). Hind wings with indistinct and rounded costal maxillary palp 2-segmented, unusually elongated, with process, vein MA not forked. Male fore tarsus usually two rows of long filtering setae (superficially similar in 1-1.3 of fore tibia. Second segment of hind tarsus dis- Oriental Choroterpides). Male imaginal genitalia with tinctly shorter than first segment. Abdominal segment a median pair of titillators and a basoventral pair of 9 dilated caudally, forceps base broad. Penis fused in prominent spines1. In imagines hind tarsal segment 1 basal half, penis lobes laterally extended with a completely articulated with tibia (tarsus clearly 5-seg- rounded median concavity on apical margin. A pair mented) and forceps with 3 small distal segments of median titillators and a pair of long pointed spines (Wang & McCafferty 1995, Ent News 106, 5: 254, basolaterally on penis stem (autapomorphy). Larvae Fig. 1), five-jointed. Arthropleidae most probably re- with three tails, terminal filament vestigial in the present a sister lineage to all genera currectly included winged stages. Larval mouthparts and feeding have in Heptageniidae NEEDHAM, 1901 (cf. Wang & been studied by Balthasar (1937, Zool. Anz. 120: McCafferty 1995, Ent News 106, 5: 251) and studies 204-230) and Froehlich (1964, Opusc. entomol. 29: of internal organs indicate the same (Landa 1973, 188-208). Subimagines similar to imagines, subimag- Proc. Ist Int. Conf. Eph., p. 155-159; Landa & Soldán inal male genitalia sufficiently developed to allow for 1985). This conclusion has been supported by several identification. For more detailed larval and imaginal cladistic analyses (e.g., Studemann et al. 1987, Bull. diagnosis see below, A. congener. Soc. Frib. Sci. Nat. 76: 144-167; McCafferty 1991, DISTRIBUTION. Holarctic. Ann. Entomol. Soc. Amer. 84: 343-360 and 1991, Overv. Strateg. Eph. Plecopt., p. 87-102) 2. Exo- BIOLOGY. Larvae occur in lakes as well as in pools and chorion of eggs finely granulated, with relatively margins of rivers and streams, usually among sub- densely distributed rounded macrogranula and evenly merged roots of sedges (Carex sp.). They feed by fil- scattered large KCT’s. Distribution: Holarctic. tering or gathering fine particulate organic detritus from the sediment and water column (the only case Arthroplea BENGTSSON, 1908 so far known of an active filtrator within Ephe mer op - tera). Life cycle of the univoltine summer (Us) type, Arthroplea BENGTSSON, 1908; K. Svenska Vet.-Akad. overwintering in the egg stage. Subimagines probably Årsbok 6: 239 emerge on leafs just above the water line. Type species: Arthroplea congener BENGTSSON, REMARKS. In Europe imagines are easily identified by 1908 (monotypy) male genitalia and egg chorionic structure. Nymphs Remipalpus BENGTSSON, 1908; K. Svenska Vet.-Akad. Års- con spicuous by long maxillary palps visible in dorsal bok 6: 242 [junior subjective synonym teste Bengtsson view. (1930, Lund. Univ. Årsskr. N.F. (2) 26: 24)] AXONOMY Potameis BENGTSSON, 1909 [pro parte: larva] ; Lunds Univ. T : Systematic position not clear, often in- Årssk., N.F., Afd. 2, 4: 14 [misidentification teste Bengts- cluded in family Heptageniidae. Larvae highly special- son (1930, Lunds Univ. Årsskr., N.F., Avd. 2, 26, 3: 24)]3 ized with numerous autapomorphies, imaginal wing Haplogenia BLAIR, 1929; Entomol. Mon. Mag. 65: 254 [ju- venation and male genitalia more similar to the hep- nior subjective synonym teste Bengtsson (1930, Lund. tageniid type but gonostyli with three distal segments. Univ. Årsskr. N.F. (2) 26: 24)] Details of male genital structure similar in some rep- DIAGNOSIS. Rather small species, wing length app. 8- resentatives of Nixe FLOWERS (see drawing in McCaf- 10 mm. Larvae dorsoventrally flattened, head dis- ferty 2008, Can. J. Arthropod Ident. 7: 42, fig. 163). tinctly broader than thorax. Mouthparts highly EXTRALIMITAL SPECIES: specialized forming a sort of filtering basket, with long Arthroplea bipunctata (MCDUNNOUGH, 1924); Occ. Pap. maxillary palps visible in dorsal view (autapomorphy). Boston Soc. Nat. Hist. 5: 76 (North America [sub Ci- nygma])

1 Male genitalia of A. bipunctata figured by Traver (in Needham et al., 1935: 425, fig. 112) indicate an additional (dorsal) pair of basolateral spines (in fact a sclerotized fold, connecting the outer penis lobe with the stem), contrary to the original description and drawing by McDunnough (1924, pl. 6, fig. 5; sub Cinygma). 2 However, molecular analyses (rRNA) suggest Heptageniidae paraphyletic and position of Arthroplea very close to some heptageniid genera (cf., e.g., Ogden & Whiting 2005, Molecular Phyl. Evol. 37: 625-643; Ogden et al. 2008, Ogden et al. 2009). 3 For Potameis BENGTSSON, 1909 [pro parte: imago, subimago]; Lunds Univ. Årssk., N.F., Afd. 2, 4: 13 [misidentification] see Para- meletus, p. 62. ARTHROPLEIDAE 243

131. Arthroplea congener transparent, faintly tinged with yellowish brown, veins BENGTSSON, 1908 brownish. Fore legs brownish, middle and hind legs yellowish brown. Abdomen brownish (more reddish Arthroplea congener BENGTSSON, 1908; K. Svenska in females), abdominal pleurae yellowish, terga with Vet.-Akad. Årsbok 6: 239 a paramedian pair of elongated light dots or streaks.

Remipalpus elegans BENGTSSON, 1908; K. Svenska Vet.- Male genitalia diagnostic (some similarities with Hep- Akad. Årsbok 6: 242 [junior subjective synonym teste tagenia and Nixe, figured in detail by Studemann et Bengtsson (1930, Lund. Univ. Årssk. N.F. (2) 26: 27) act- al. 1987: 152-156, figs 124-132). Forceps five-seg- ing as First Reviser, ICZN (1999) Art. 24.2.2.] mented, three subequal distal segments app. as long Arthroplea congener BENGTSSON, 1908; apud Bengtsson as half of second segment. Apical segment slightly (1909, Lunds Univ. Årsskrift. N.F. Afd. 2, 5 (4): 18 [re- shorter than penultimate segment, rounded distally. description] Forceps base broad, with two large conical processes Potameis elegans BENGTSSON, 1909 [pro parte: larva] ; laterally, straight or shallow concave in middle. Penis Lunds Univ. Årssk., N.F., Afd. 2, 4: 14 [misidentification teste Bengtsson (1930, Lunds Univ. Årsskr., N.F., Avd. 2, fused in basal half. Penis lobes flattened, apically 26, 3: 24)]4 rounded with a distinct round mediodistal incision. Cinygma mirabile ARO, 1910; Viipuri p. 16 [junior subjec- Outer penis lobe with a strong subapical spine dorsally tive synonym teste Bengtsson (1930, Lund. Univ. and an oblique sclerotized fold, running towards the Årsskrift. N.F. (2) 26: 27)] penis stem. Ventral side of penis stem basolaterally Cinygma mirabile ARO, 1910 [junior subjective synonym with a long spine. Cerci yellowish with brownish an- teste Tiensuu (1939, Suomen Hyonteistiet 5: 106)] nulation. Female imagines lighter with a reddish tinge. Haplogenia southi BLAIR, 1929; Entomol. Mon. Mag. 65: Subgenital plate blackish, semicircular, subanal plate 255 [junior subjective synonym teste Bengtsson (1930, slightly elongated and apically broadly rounded. Exo- Lund. Univ. Årsskrift. N.F. (2) 26: 27)] chorion of eggs finely granulated, with densely distrib- Arthroplea frankenbergeri BALTHASAR, 1937; Zool. Anz. 120: 208 [junior subjective synonym teste Landa (1969, uted rounded macrogranula and scattered KCT’s. Fauna SSR 18, p. 151)] DISTRIBUTION. Palaearctic. In Europe a conjunctive Arthroplea congener BENGTSSON, 1908; apud Studemann et al. (1987, Bull. Soc. Frib. Sci. Nat. 76: 144) [redescrip- area (subarea) in Fennoscandia and Northern Russia tion, egg chorionic structure] (extending to Western Siberia). Disjunctive area (sub- areas) in Great Britain and Central Europe – Austria LARVA. Body length 8-10 mm. Head and body (Oberösterreich, Nordwald), Czech Republik, Ger- dorsoventrally flattened. Compound eyes large, situ- many (Saxonia), Slovakia (the Danube lowland only) ated dorsally. Labrum rather broad and short, slightly and southern Poland (northern slopes of the Carpathi- bent laterally. Mandibles inverted (right mandible with ans). In general distribution roughly following the distally projecting mola). Maxillary palps and labial southern limits of the last glaciation (Würm), termed palps two-segmented, the former extremely elongated “nördliche Gletscherrand-Art” according to Zimmer- and with two rows of long filtering setae. Glossae and mann (1975). In Fennoscandia only exceptionally out- paraglossae long, sickle-shaped. Hypopharyngeal lin- side the lowlands. In Central Europe from about 100 gua circular, superlingae relatively short, rounded tri- m a.s.l. (localities near Bratislava in Slovakia, angular and slightly bent backwards. Femora with Balthasar 1937 [sub A. frankenbergeri]) to about 800 stout bluntly pointed bristles, tarsal claws usually with m a.s.l. (in the Šumava Mts., Czech Republic, Soldán 3 teeth. Seven pairs of single plate like gills (filamen- et al. 1998, Soldán & Zahrádková 2000). Represent- tous part missing). Gills roughly heart-shaped, asym- ing a Ural (Haybach (1998: 217) or tundral faunistic metrical, with conspicuous dark tracheization. element (Jacob 1972, Dissert. Univ. Leipzig, p. 93), Posterior margin of terga with a row of long slender boreotundral according to Haybach & Jacob (2010, spines, abdominal segments 2-9 with small postero- Lauterbornia 71: 88). Type locality is Lesjöfors, lateral spine. Cerci and paracercus with small spines Värmland Province, Sweden. and long bristles, a row of fine long setae on internal side of cerci. BIOLOGY. Larvae inhabit stillwater or slow flowing sec- tions of rivers, where they are usually found between SUBIMAGO. Similar to imago, colouration dull yellowish submerged roots of Carex and other submerged brown. plants feeding on detritus (including microscopic Crus- IMAGO. Length of fore wing 9-11 mm. Male com- taceans and Rotatoria). Frequency and periodicity of pound eyes dark brown, separated in the middle by a strokes of maxillary palps have been described by Sol- narrow gap. Thorax dorsally pitch-brown. Wings dán (1978, Acta Entomol. Bohemoslov. 76: 300-

4 For Potameis elegans BENGTSSON, 1909 [pro parte: imago, subimago]; Lunds Univ. Årssk., N.F., Afd. 2, 4: 13 [misidentification] see Parameletus chelifer, p. 62.