Procloeon (Oculogaster) regularum Müller-Liebenau & Hubbard 1985

Kluge, Nikita J., 2020, Review of Oculogaster Kluge 2016 (Ephemeroptera, Baetidae, Procloeon Bengtsson 1915), Zootaxa 4820 (3), pp. 401-437 : 423-428

Procloeon (Oculogaster) regularum Müller-Liebenau & Hubbard 1985

( Figs 84–108 )

Procloeon regularum Müller-Liebenau & Hubbard 1985: 550 (larva).

Material examined ( ZIN). SRI LANKA: border of Uva and Central provinces: tributary of river Uma near Randenigala dam, 7°11′20′′N 80°56′30′′E, 13–14.I.2011, coll. N. Kluge & L. Sheyko: 1 larva ; Uva province, Haputale , 15–23.I.2011, coll. N. Kluge & L. Sheyko: 1 L-S-I ♂ , 2 L-S ♂, 1 L-S/I ♀; Central province, Ginigathhena (17 km N Hatton), 31.I–3.II.2011, coll. N. Kluge & L. Sheyko: 1 I ♂ ; Sabaragamuwa province, Dalhausie near Sri Pada ( Adam’s Peak ), river Seetha Gangula , 26.I.2011, coll. N. Kluge & L. Sheyko: 1 S-I ♂ , 2 I ♀; Dalhausie near Sri Pada ( Adam’s Peak ), river Seetha Gangula close to guesthouse «Vegetable Garden», 6°49′34′′N 80°31′29′′E, 214.II.2020, coll. N. Kluge & L. Sheyko: 8 L-S-I ♂ , 13 L-S-I ♀, 1 L-S ♂, 55 I ♀, 11 L ♂, 50 L ♀.

Descriptions. Larva. CUTICULAR COLORATION. Head with brownish and colorless areas. Pronotum and mesonotum ocher or brownish with lighter and darker areas; cuticle of fore protoptera either nearly unicolor, or with lighter stripes along concave veins. Metanotum and thoracic pleura with colorless and brown areas, thoracic sterna colorless. Legs colorless or brownish. either unicolor, or with diffusive brown band in distal part of femur and with tarsus darkened. Abdominal terga with variable maculation, different on different segments; most or all terga with submedian pair of blanks, either corresponding to sigilla, or larger than sigilla; tergum IV more or less lighter than others, tergum VI darker than others ( Figs 84, 89 ; Müller-Liebenau & Hubbard 1985: fig. 17). Abdominal sterna lighter than terga, either unicolor, or with lighter and darker areas. Caudalii ocher with posterior margin of each 4th segment brown ( Fig. 85 ).

HYPODERMAL COLORATION. Mature larvae of both sexes with pair of reddish or brownish spots on each tergum IV and VII ( Fig. 89 ) (as in winged stages—see below).

SHAPE AND SETATION. Mouth parts as in original description; maxillary palp 3-segmented, with 2nd and 3rd segments subequal ( Müller-Liebenau & Hubbard 1985: fig. 9a–e). Femora with very small spine-like setae on outer and inner sides, with 2 spine-like apical setae located in plane of leg ( Müller-Liebenau & Hubbard 1985: fig. 9f). Claws moderately long, in proximal part with two rows of minute denticles increasing in size distally ( Müller-Liebenau & Hubbard 1985: fig. 9g). Hind protoptera completely absent ( Müller-Liebenau & Hubbard 1985: fig. 9h). 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 sparse small spine-like pointed denticles; posterior margins of terga II–X with spine-like pointed denticles of unequal length; on all terga, including tergum IX, row of denticles not interrupted medially. Abdominal terga with short scales in wide semilunar or W-shaped non-opercula-bearing sockets, with sparse simple fine setae and paired bifurcate sublateral setae on some of posterior segments. Posterior margins of abdominal sterna I–IV or I–III smooth, posterior margin of sternum V or sterna IV–V with few minute denticles, posterior margins of sterna VI–IX and paraprocts with spine-like pointed denticles of unequal length. 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 regular rows. Tergalii widest near base, without dorsal lamellae; costal rib without denticles; tergalii III–VII each with very fine additional middle rib located just anteriad of main trachea ( Figs. 90–96 ). In distal part of cercus spine on outer side of each segment as long as combined length of 2½ next segments ( Fig. 86 ).

Subimago. CUTICULAR COLORATION. Cuticle either completely colorless, or with pronotum slightly maculated and few lateral thoracic sclerites tinged with brownish ( Figs 107–108 ).

HYPODERMAL COLORATION. As in imago (see below, male and female).

TEXTURE. On fore leg of male and female, 1st tarsal segment covered partly with microtrichia (as tibia), partly with pointed microlepides; all other tarsal segments entirely covered with pointed microlepides ( Figs 105–106 ).

Imago, male ( Figs 99–102 ). Head ocher or whitish. Antenna with scapus and pedicellus non-pigmented, flagellum either non-pigmented, or brown. Turbinate eyes widened apically; facetted surface either yellow, or orange and bordered with narrow yellow ring either whitish-red. Thorax ocher or whitish. Legs pale ocher. In specimen from Haputale, ratio femur / tibia / tarsal segments (mm) on fore leg 1.17: 1.45: 0.05: 0.48: 0.40: 0.17: 0.16; on middle and hind legs 1.02: 1.08: 0.44: 0.17: 0.05: 0.15. Middle and hind legs each without apical spine on 1st+2nd tarsomere, with single apical spine on primary 3rd tarsomere (as in Fig. 105 ). Fore wing with membrane colorless, longitudinal veins ocher, cross veins darker. Pterostigma with 2–3 oblique veins, no other veins in costal field; marginal intercalary present in each interspace. Hind wing absent. Abdominal terga and sterna translucent, ocher or white; tergum IV with pair of sublateral orange or red-brown maculae; most part of tergum VII colored with red-brown; tergum VIII with orange or red-brown marking; terga IX–X either entirely white or ocher, or with orange markings. Genitalia non-pigmented. Median projection of penial bridge rounded ( Fig. 97 ). Cerci whitish.

Imago, female ( Figs 103–104 ). Head moderately wide, distance between eyes subequal to eye length; eyes significantly elevated above head surface ( Fig. 103 ). Head ocher. Pronotum ocher, either unicolor, or with variable unpaired brown spots. Thorax ocher or whitish. Legs as in male (see above); fore leg without apical spine on 2nd tarsomere, with single apical spine on primary 3rd tarsomere (as in Fig. 106 ); same on middle and fore legs (as in Fig. 105 ). Wings as in male (see above). Abdomen ocher, each tergum I–VII or I–VIII laterally with pair of dark brown or black oval spots; each tergum IV and VII with pair of large orange or red-brown spots adjacent to lateral darker spot of same segment. Sterna without spots. Cerci whitish (as in male).

Egg. Without rigid chorion (viviparity).

Dimension. Fore wing length 5.5–6 mm.

Larval habitat. In the river Seetha Gangula, most larvae were collected from a shallow place with sandy bottom and slow water current.

Development of females. In the river Seetha Gangula, males are much less numerous than females: among 82 larvae collected there in 2020, 19 individuals are males, and 63 are females. In spite of this, females appear to require fecundation for development of embryos; 11 female imagines were kept alive for 5–10 days after hatching from subimago, but their ovicells did not start to develop into embryos. An ultraviolet lamp placed near this river attracted only females free from embryos; all 55 specimens of P. (O.) regularum collected with help of this lamp are female imagines with not a single embryo inside; not a single subimago, nor male of this species was attracted to this lamp.

Distribution. Sri Lanka.

Figures

FIGURES 84–89. Larvae of Procloeon (Oculogaster) regularum. 84–88, exuviae: 84, abdomen; 85–86, its caudalii; 87–88, fragment of middle part of cercus, with focus on lateral and median sides; 89, male larva.

FIGURES 90–98. Procloeon (Oculogaster) spp. 90–97, P. (O.) regularum: 90–96, tergalii I–VII; 97, genitalia of male imago (penis dotted, muscles not shown). 98, tergalius IV of Procloeon (Oculogaster?) sp. «Philippines».

FIGURES 99–102. Male imagines of Procloeon (Oculogaster) regularum. 99–101, general view; 102, abdominal tergum IV.

FIGURES 103–108. Females of Procloeon (Oculogaster) regularum. 103–104, imagines; 105–108, subimaginal exuviae: 105–106, middle and fore tarsi (arrows show spines; 1st–5th, initial tarsomeres); 107, half of mesonotum; 108, mesothoracic pleuron.