Deanophlebia, Finlay, 2019

Finlay, K. J., 2019, Deanophlebia: A new genus of south-eastern Australian mayflies and subsequent redefinition of the subgenus Nousia (Australonousia) (Ephemeroptera: Leptophlebiidae), Zootaxa 4668 (1), pp. 30-50 : 30-50

Deanophlebia gen. nov.

Type species. Atalophlebia kala (Harker)

Distribution. Southern New South Wales, Eastern Victoria.

Diagnosis. Male imago. Dimensions: average body length 10.9mm, average forewing length 11.7mm, average hindwing length 2.5mm, hindwing length approximately one-fifth forewing length. General body colour brown, head dark brown, antennae tan to dark brown. Eyes: upper eye size large, sometimes contiguous. Thorax: brown to shiny brown with darker markings. Legs: forelegs with femora tan brown with darker apices, tibiae and tarsal golden. Wings. Forewing: membrane hyaline, longitudinal and crossveins pigmented, anal veins yellow, costal veins present in proximal and distal halves of wing; costal space with more than 20 crossveins throughout, forewing MA forked at half to slightly more than half the distance from base to wing margin; ICu 1 recurved to join CuA; CuA and CuP linked by crossvein; ICu 1 and ICu 2 parallel as wing margin approached. Hindwing: mostly hyaline, costal space slightly opaque; costa joins subcosta at approximately four-fifths wing length; no crossveins in proximal halves of costal space; hindwing MP forked with intercalary. Abdomen: light to tan brown with golden and darker brown markings, colour and patterning variable. Genitalia: forceps three segmented; tan brown, progressively lighter apically, terminal segment angular, about the same length as middle segment. Penes golden to tan brown, fused in basal half dorsally and in basal two-thirds ventrally; lobes bulbous and expanded laterally at half total length, then concave until apex where lobes expanded laterally and contiguous, small triangular process present apically; two pairs of small internal spines. Female imago. Dimensions: average body length 11.3mm, average forewing length 12.3mm, average hindwing length 2.6mm, hindwing length approximately one-fifth forewing length. General patterning and colour similar to male. Wings. Forewing: colour and venation similar to male except with with generally more crossveins on average throughout costal and subcostal spaces. Abdomen: sternum nine moderately cleft. Egg. Ovoid; polar cap absent, chorion with large and small circular shaped protuberances over surface, pattern variable. Male and female subimago. General pattern and colouring similar to imago. Wings uniformly grey-brown, opaque. Mature nymph. Dimensions: average body length male 11.5mm, average body length female 12.4mm. General colour tan brown with darker markings. Head: prognathous; tan to dark brown, head width 0.9 times width of pronotum. Eyes: upper lobes of male orange to reddish-brown, lower lobes black; eyes of female black. Mouthparts. Labrum and clypeus: lateral margins of clypeus very slightly diverging towards anterior; labrum slightly wider than clypeus, lateral margins rounded; anterior margin of labrum straight with no apparent antero-median emargination; labrum width approximately 2.2 times labrum length; five elongated denticles present on anterior margin extending one fifth to one half the total width of labrum, frontal setae arranged as a broad band; secondary hair fringe clearly separated from broad band. Mandibles: outer margins slightly curved. Left mandible: two incisors, each with three apical teeth, outer incisor inconspicuously serrated on inner lateral margin, prostheca stout, prosthecal tuft slender with hairs on lateral margins only. Right mandible: spine-like setae on inner lateral margin, two incisors, outer incisor with three apical teeth, inconspicuously serrated on inner lateral margin, inner incisor with two apical teeth, prostheca slender, prosthecal tuft slender with hairs on lateral margins only. Maxillae galea-lacinae as wide as long, subapical row of 16–23 pectinate setae; palpi extending just beyond galea-lacinae. Hypopharynx: well developed lateral processes, anterior margin of lingua deeply cleft. Labium: glossae not turned under ventrally; terminal palp segment with row of triangular spines almost circling apex and stout spines on dorsal surface; submentum with spines on lateral margins. Thorax: tan brown with darker brown markings. Legs: golden to tan brown, femora usually darker at apices. Abdomen: golden to tan brown with golden and darker brown markings, colour and patterning variable; posterolateral spines prominent on segments two to nine, progressively larger posteriorly. Gills: membrane clear or opaque, light grey to grey-black colour; present on segments one to seven, double, upper and lower lamellae equally developed; each gill tapered to a thin point apically; main and lateral tracheae present, strongly developed. Caudal filaments: three; golden; terminal filament longer than cerci.

Etymology. The genus is named after John Dean who first characterised the nymphs.

Remarks. The genus Deanophlebia is established for two Nousia (Australonousia) morphospecies described in Dean (1999). Nousia sp. AV3 (Australian Voucher 3) was determined to belong to Nousia (Australonousia) from the similarities in mouthpart, leg and gill morphology of the nymph ( Dean 1999) but was not formally described as the adults were unknown. Nousia sp. AV 3 specimens reared in the laboratory to adulthood, confirmed an association between nymph and imago.

Upon examination of a reared imago it became clear that the adult had been previously described as Atalophlebia kala by Harker (1954) from specimens collected by R J Tillyard in the lakes of Kosciusko National Park in 1930. The holotype and type slide of genitalia from the NHM (see Harker 1954, FIG. 36 , p. 251) reconciled with the genitalia of the reared specimens of Nousia sp. AV3.

Harker (1954) described only the adult stages and the basis for the inclusion of this species in Atalophlebia is not clear. The nymphs of Nousia sp. AV3 are morphologically different from Atalophlebia . In particular, Dean (1999) suggested that all Atalophlebia species possess gills with the margins of the lamella divided to form three or more digits. Examination of all life stages of Nousia sp. AV3 led to the conclusion that the species belongs in neither Atalophlebia nor Nousia and a new genus was warranted leading to the new combination: Deanophlebia kala (comb. nov).

Dean (1999) also recognised Nousia sp. AV11 as a morphospecies of the subgenus Nousia (Australonousia) . As before, no association with adults had been made at the time. Collections of the species by the author from headwater streams in and around Falls Creek, Victoria were reared to adulthood in the laboratory and closely resembled Deanophlebia kala , but with enough differentiation for the erection of a new species: Deanophlebia radsjoshi (sp. nov.), which is described in full in this paper.

The genus Deanophlebia can be distinguished all other genera in Leptophlebiidae by the following combination of characters. In the imago: (i) average male and female body length more than 10mm; (ii) male upper eyes large, sometimes contiguous; (iii) average male and female forewing length more than 10mm; (iv) forewing costal crossveins present both proximally and distally in costal and subcostal space, more than 20 crossveins in coastal space; (v) forewing MA forked at half to slightly more than half the distance from base to wing margin; (vi) ICu 1 recurved to join CuA; (vii) CuA and CuP linked by crossvein; (viii) ICu 1 and ICu 2 parallel as wing margin approached; (ix) hindwing subcostal vein four-fifths maximum length of wing; (x) hindwing with no crossveins in proximal half of costal space, more than five in distal costal space, more than five throughout subcostal space; (xi) hindwing MP forked with intercalary; (xii) penes fused in basal half dorsally and in basal two-thirds ventrally; lobes bulbous and expanded laterally at half total length, then concave until apex where lobes expanded laterally and contiguous, small triangular process present apically, two pairs of small internal spines; (xiii) female sternum nine moderately cleft; (xiv) egg ovoid, polar cap absent, chorion with small circular shaped protuberances irregularly interspersed with larger ones.

In the mature nymph: (i) average male and female body lengths more than 10mm; (ii) labrum slightly wider than clypeus, lateral margins rounded; (iii) margins of clypeus very slightly diverging towards anterior; (iv) labrum more than two times wider than length along median line; (v) anterior margin of labrum straight with no apparent antero-median emargination; (vi) labrum with five elongated denticles on anterior margin extending one-fifth to one-half the total width of labrum; (vii) mandibles with outer margins slightly curved; left mandible with prostheca stout, prosthecal tuft slender with hairs on lateral margins only; (viii) maxillae galea-lacinae slightly wider to as wide as long; (ix) labium glossae not turned under ventrally and lying in the same plane of paraglossae; (x) hypopharynx with well-developed lateral processes, anterior margin of lingua deeply cleft; (xi) fore tarsi with 11-15 ventral teeth, progressively larger apically, apical denticle much larger; (xii) abdomen with prominent post lateral spines on segments two to nine; (xiii) gills alike, lamellae slender; main and lateral tracheae strongly developed.

Figures

FIGURES 32–36. Deanophlebia radsjoshi. Female imago: Fig. 32. Forewing showing relative size of hindwing, scale bar 1mm; Fig. 33. Hindwing, scale bar 500 µm; Fig. 34. Ventral view of abdomen, sternites seven to nine, scale bar 500µm; Fig. 35. SEM of egg, scale bar 50 µm; Fig. 36. SEM detail of egg chorion, scale bar 10µm.