Procloeon (Oculogaster) album, Kluge, Nikita J., 2016

Kluge, Nikita J., 2016, A new subgenus Oculogaster subgen. n. for viviparous representatives of Procloeon s. l., with discussion about status of the generic name Austrocloeon Barnard 1932 and the species name africanum Esben-Petersen 1913 [Cloeon] (Ephemeroptera, Baetidae), Zootaxa 4107 (4), pp. 491-516 : 506-514

Procloeon (Oculogaster) album sp.n.

( Figs 43–79 )

Material examined. Holotype: L/S♀, THAILAND, Kanchanaburi Province, Erawan Falls, 2–4.II.2015, coll. N. Kluge & L. Sheyko. Paratypes: the same locality and dates, 1 L/S♂, 3 L/S♀, 2 S-I♂, 2 I ♂, 1 S♂, 2 I ♀ (filled with embryos).

Descriptions. Larva. CUTICULAR COLORATION. Head light with pale brownish markings, frons with pair of contrasting brown longitudinal stripes. Pronotum and mesonotum ocher with diffusive brown maculation; cuticle of fore protoptera nearly unicolor ocher, with diffusive brown macula at base ( Fig. 68 ); veins either not expresses, or visible as stripes slightly lighter than background. Metanotum and thoracic pleura with colorless and brown areas, thoracic sterna colorless. Legs colorless, femora with diffusive brown band in distal part. Abdominal terga with ocher, brown and colorless areas; terga II and VI the darkest, tergum III with pair of submedian round brown maculae close to anterior margin, tergum VIII with pair of especially dark brown maculae at latero-posterior angles ( Figs 68, 70 ). Abdominal sterna I–VIII colorless with diffusive brownish maculae laterally, sternum IX with brownish maculation. Caudalii ocher with posterior margin of each 4-th segment brown ( Fig. 59 ).

HYPODERMAL COLORATION. Mature male and female larva with reddish or brown spots on abdominal terga, as in winged stages ( Figs 68, 70 ).

SHAPE AND SETATION. Mandibles with incisor and kinetodontium fused more than to middle, with ventral denticle well-developed; incisor of right mandible with 2nd denticle longest; right prostheca apically with 4–10 short diverging processes ( Figs 44–45 ). Maxillary palp 3-segmented ( Fig. 46 ). Labium with glossae and paraglossae of subequal size, palp with median angle moderately projected ( Figs 47–48 ). Femora with very small spine-like setae on outer and inner sides, with 2–4 larger pointed spine-like setae on outer side near apex (their number equally varies on all leg pairs) ( Fig. 56 ). Claws moderately long, with two rows of minute denticles in proximal part only ( Fig. 57 ). Hind protoptera completely absent. Abdominal segment IX with 3–6 lateral spines on each side, other segments without lateral spines; postero-lateral spines present on segments II–IX, being minute on anterior segments. Posterior margin of abdominal tergum I with few small sparse spine-like pointed denticles; posterior margins of terga II–X with larger spine-like pointed denticles of unequal length; tergum X with sublateral denticles longest ( Fig. 61 ). Abdominal terga with short scales in wide W-shaped non-operculated sockets, with sparse simple fine setae ( Fig. 62 ). Posterior margins of abdominal sterna I–IV smooth, sternum V with few small denticles, posterior margins of sterna VI–IX with regular equal triangular denticles; paraprocts with longer denticles ( Fig. 58 ). Abdominal sterna with sparse scales and sparse fine setae; in lateral areas of sterna both simple and bifid fine setae vary from small to very long, located sparsely and irregularly, not forming rows or groups ( Fig. 63 ). Tergalii without dorsal lamella; costal rib without denticles; tergalii I and II triangular, widest at mid-length, with pointed apex; tergalii III–VI widest near base ( Figs. 49–55 ). Tergalii II–VI or III–VI with very fine additional middle rib located just anteriad of main trachea ( Figs 51–54 , 64 ). In distal part of cercus spine on outer side of each segment as long as 3 next segments ( Fig. 60 ).

Subimago. CUTICULAR COLORATION. Cuticle entirely colorless.

HYPODERMAL COLORATION. Maculae on abdominal terga as in imago, but smaller and red (unlike black in imago).

TEXTURE. On fore leg of male and female 1st tarsal segment covered mainly with microtrichiae (as tibia), at apex with pointed microlepides; all other tarsal segments entirely covered with pointed microlepides.

Imago, male. Head whitish-ocher. Turbinate eyes widened at apex, either white ( Figs 73–74 ), or orange ( Figs 72 , 75 ). Thorax either entirely whitish ( Figs 72–74 ), or with irregular purplish markings ( Fig. 75 ). Legs pale ocher or whitish. Ratio femur / tibia / tarsal segments on fore leg 95:130:5:57:40:21:14, on middle and hind leg 80:75:40:12:3:12. Middle and hind legs without apical spine of 1st+2nd tarsomere, with single apical spine on primary 3rd tarsomere. Fore wing widest at mid-length, narrower proximally; membrane and veins colorless; pterostigma with one oblique vein, no other veins in costal field; marginal intercalary present in each space ( Fig. 67 ). Hind wing absent. Abdominal terga and sterna translucent, either white, or glass-like; tergum IV with pair of contrasting brown-black round maculae; terga VII and VIII dorsally at most contrastingly colored with red and brown-black, with pair of more or less separated red or brown spots on postero-lateral angles; tergum IX not colored, as white as segments I–III and IV–V; tergum X white with pair of intensive lemon-yellow or orange spots. Genitals non-pigmented. 1st segment of gonostylus on ventral side swollen distally; penis truncate ( Fig. 65 ). Cerci colorless.

Imago, female ( Figs 76–79 ). Head relatively wide, distance between eyes exceeds eye length; eyes only slightly elevated above head surface. Head and thorax colorless with white and intensive yellow. All leg with single apical spine on primary 3rd tarsomere. Wings as in male. Abdomen whitish, with following contrasting maculae: lateral pairs of contrasting small black spots on sides of terga II, IV, VII and VIII; more median pair of contrasting larger black spots on tergum IV, pair of lighter brown maculae on tergum VII and pair of orange spots on tergum X.

Egg. Without rigid chorion; embryos are developed inside female imago, so that mature female imago looks maculated because of black eyes and ocelli of embryos visible through its integument ( Figs 76–79 ).

Dimension. Fore wing length of male and female 4.3 mm.

Association of larvae and imagoes. Larvae, subimagoes and imagoes were collected in the same place: winged stages were collected from lamps on a small bridge across the Erawan River, and larvae were collected in the river near this bridge. This fact itself is fare not enough to associate these stages, because at the same place many mayfly species were collected, among which 4 other new species of Procloeon (see Table 1 ). In spite of the fact that no one imago of P. ( O.) album sp.n. is reared from larva, association of imagoes and larvae is made for certain by comparison of larvae ready to molt to subimago with subimagoes and imagoes. All four male imagoes, male subimago and male subimago extracted from larva have the same unusual color pattern of abdomen, consisted of a pair of maculae on tergum IV, colored median part of terga VII–VIII and latero-posterior spots on terga VII–VIII, wile tergum IX is colorless ( Figs 70–73 ). Both female imagoes and all four female subimagoes extracted from larvae have characteristic color pattern of abdomen, consisted of a pair of round spots on tergum IV and pairs of smaller more lateral spots on terga II, IV, VII and VIII ( Figs 68–69 , 76–77 ). Subimaginal wing extracted from mature larva (holotype), treated by alkali and spread on slide, has one vein in pterostigma, that is characteristic for Oculogaster. All four mature larvae, being ready to molt to subimago, have soft eggs without rigid chorion, that testifies about their viviparity.

Comparison. Recently, only 4 species of Procloeon are formally described from Indochina: Procloeon spinosum Nguyen & Bae (in Tungpairojwong & Nguyen & Bae) 2006 , Procloeon narumonae Tungpairojwong & Bae 2015 , Procloeon rubeosternum Tungpairojwong & Bae 2015 and Procloeon siamensis Tungpairojwong & Bae 2015 ; larva of the new species differs from all these species by complete absence of dorsal lamella on tergalii of all pairs. Some other larval characters are shown on Table 1 .

Figures

FIGURES 43 – 48. Procloeon (Oculogaster) album sp. n., larva. 43, labrum, 44, 45, apices of left and right mandibles; 46, maxilla, dorsal view; 47, half of labium, ventral view; 48, the same, dorsal view. Abbreviations: ds 1, ds 2, ds 3, dentisetae; in 1, in 2, in 3, in 4, denticles of incisor; in-V, ventral denticle of incisor; kd 1, kd 2, kd 3, denticles of kinetodontium.

FIGURES 49 – 58. Procloeon (Oculogaster) album sp. n., larva. 49 – 55, tergalii I – VII; 56, fore leg, anterior view (fine setae not shown; dots show bases of fine setae forming regular rows on apical part of femur, proximal part of tibia and proximal part of tarsus); 57, claw; 58, paraproct (49 – 52, 54 – 55, 58, holotype).

FIGURES 59 – 64. Procloeon (Oculogaster) album sp. n., larva. 59, paracercus and cercus (with subimaginal cercus inside); 60, distal part of cercus; 61, posterior margin of abdominal tergum X; 62, fragment of abdominal tergum III; 63, fragment of abdominal sternum VI; 64, tergalius VI (arrow shows additional middle rib) (59, 60, holotype).

FIGURES 65 – 67. Procloeon (Oculogaster) album sp. n. 65, genitals of male imago (at left half gonovectal muscles shown by interrupted lines, hidden part of penis shown by interrupted line and dotted, gonostylar muscle not shown; at right half gonostylar muscle shown by interrupted lines, gonovectal muscles not shown; median styligeral muscle shown by interrupted lines, areas of anterior attachment of median paraproctal muscles shown by dotted lines). 66, genitals of male subimago; 67, wing. Abbreviations: 1, 2, 3, segments of gonostylus; mIX-X, areas of anterior attachment of median paraproctal muscles (i. e., muscles going from sternum IX to common base of paraprocts); usg, unistyliger.

FIGURES 68 – 72. Procloeon (Oculogaster) album sp. n. 68, mature female larva (reddish paired hypodermal spots on abdominal terga IV, VII and VIII visible through cuticle); 69, subimaginal abdomen extracted from mature female larva (holotype); 70, mature male larva (reddish hypodermal markings on abdominal terga IV, VII and VIII visible through cuticle); 71, subimaginal abdomen extracted from this larva; 72, male imago.

FIGURES 73 – 75. Procloeon (Oculogaster) album sp. n., male imago. 73 – 74, the same specimen at different light; 75, head and thorax of another specimen.

FIGURES 76 – 79. Procloeon (Oculogaster) album sp. n., female imago. 76, 77, lateral and dorsal view; 78, 79, part of prothorax and part of abdomen with black eyes and ocelli of embryos visible through integument.