Riekophlebia, Christidis, Faye, 2009

Christidis, Faye, 2009, Riekophlebia crocina, a new genus and species of Atalophlebiinae (Ephemeroptera: Leptophlebiidae) from the Wet Tropics bioregion of north-eastern Australia, Zootaxa 2063, pp. 64-68 : 65-66

Riekophlebia gen. n

Type species. Riekophlebia crocina sp. n

Diagnosis. Imago. Wings hyaline ( Fig. 1 ). Forewing length-width ratio 3.0–3.2; MA forked at just over half distance from base of vein to margin of wing, fork symmetrical; MP2 attached to MP1 at about 0.24 length of MP1; ICu1 not attached at base to CuA-CuP cross vein. Hind wing 0.18–0.20 times length of forewing; costal margin convex; vein Sc about 0.8 length of hind wing ( Fig. 2 ). Tarsal claws dissimilar, one with an apical hook, the other pad-like. Male genitalia with claspers 3 segmented, segment 1 of claspers narrowing at about 0.4 of length; penes fused along most of their length, each lobe with a large ventral spine near apex; styliger plate with deep cleft ( Fig. 4 ). Female ninth sternum entire, pointed apically ( Fig. 5 ).

Nymph. Head prognathus. Antennae about two times length of head. Mouthparts as in Figures 6–11 . Labrum broader than clypeus; length 1.18–1.20 times maximum length of clypeus; labrum broadest beyond midlength; anterior margin with median U-shaped notch; dorsal surface with two setal fringes ( Fig. 6 ). Clypeus with lateral margins slightly divergent apically. Outer margin of mandible with small median setal tuft and series of fine setae between tuft and outer incisor ( Fig. 7 ); incisors slender; prostheca well developed. Maxilla broad apically, with 25–27 subapical pectinate setae ( Fig. 8 ). Ligula of hypopharynx with well developed lateral processes, anterior margin cleft ( Fig. 9 ). Labium with glossae on about the same plane as paraglossae. Lateral margins of submentum with a few basal setae ( Fig. 10 ). Labial palp with segments 1 and 2 subequal in length, segment 3 about half length of segment 2. Tarsal claws with ventral teeth, increasing in size apically. Abdomen with posterolateral spines present on segments 2–9; lateral margins of abdominal segments bare, without setae. Gills present on segments 1–7; each gill lanceolate, lateral tracheae moderately developed ( Fig. 13 ). Caudal filaments 1.5 to 2 times length of body; each segment with apical whorl of spines and short setae.

Remarks. Riekophlebia can be distinguished from all other leptophlebiid genera by the following combination of characters. Imago: (1) penes fused along most of their length, each lobe with large ventral spine near apex; (2) segment 1 of claspers narrowing at about 0.4 of length; (3) styliger plate with deep cleft; (4) tarsal claws dissimilar; (5) female ninth sternum entire and pointed apically. Nymph: (1) anterior margin of labrum with median U-shaped notch; (2) labrum length 1.18–1.20 times maximum length of clypeus (3) labrum broadest beyond midlength; (4) maxillae broad apically, with 25–27 subapical pectinate setae; (5) lateral margins of submentum with a few basal setae; (6) abdomen with posterolateral spines present on segments 2–9; (7) lateral margins of abdominal segments without setal fringe; (8) gills with lateral tracheae. Riekophlebia is a member of the Meridialaris lineage as defined by Pescador and Peters (1980) and Christidis (2005), based on the possession of the following synapomorphic character states: adult tarsal claws dissimilar; ninth abdominal sternum of female entire; labrum of nymph with U-shaped notch on anterior margin; labrum broader than clypeus; maxilla broad apically; lateral margins of submentum with few basal setae. Other Australian members of the Meridialaris lineage include the genera Austrophlebioides , Kirrara , Tillyardophlebia and Manggabora .

Riekophlebia most closely resembles Tillyardophlebia and Manggabora , but can be distinguished from these genera as follows. Riekophlebia is separated from Manggabora in the imago by the deep cleft on the posterior margin of the styliger plate, and absence of a large ventral projection on the penes; and in the nymph by the presence of posterolateral spines on abdominal segments 2–9, a maxilla with 25–27 subapical pectinate setae, and presence of setae on the outer margin of mandible between the median setal tuft and the outer incisor. Riekophlebia is distinguished from Tillyardophlebia by the form of the male genitalia including penes that are fused along most of their length, presence of large ventral spine near apex of each penes lobe, absence of a pair of large curved ventral spines near base of penes, and a styliger plate with a deep cleft. The nymph of Riekophlebia is distinguished from T. dostinei by the presence of lateral tracheae on the gills; and from T. alpina and T. rufosa by the form of the labrum which in Riekophlebia is broadest beyond midlength and has angular lateral margins whereas in T. alpina and T. rufosa is broadest at about midlength and has rounded lateral margins.

Etymology. This genus is named for Edgar Riek, in recognition of his contribution to mayfly research in Australia. Gender, feminine.

Figures

FIGURES 1 – 5. Riekophlebia crocina. Male imago: (1) wings; (2) hind wing; (3) abdominal terga 3 – 5; (4) penes and claspers, ventral view. Female imago: (5) ninth abdominal sternum.

FIGURES 6 – 13. Riekophlebia crocina. Nymph: (6) labrum and clypeus; (7) right mandible; (8) maxilla, ventral view; (9) hypopharynx; (10) labium, dorsal view left of midline and ventral view right of midline; (11) segment 3 of labial palp, dorsal view; (12) foreleg; (13) abdominal gill.