Procloeon (Oculogaster) niger, Kluge, 2020

Kluge, Nikita J., 2020, Review of Oculogaster Kluge 2016 (Ephemeroptera, Baetidae, Procloeon Bengtsson 1915), Zootaxa 4820 (3), pp. 401-437 : 414-420

Procloeon (Oculogaster) niger sp. n.

( Figs 43–77 )

Etymology. Allusion to the uniformly dark coloration of larva and uniform dark color pattern on abdominal terga in male and female imago.

Material examined. Holotype ( AM): L-S-I ♂ {specimen [XVIII](3)2019}, SOUTH AFRICA, Garden Route district (= Eden district ), lodge «Wild Spirit», tributary of Bobbejaans River (5 km NW Nature’s Valley). 33°57’S 23°31′30′′E, 3rd pool from waterfall, 7.II.2019, coll. N. Kluge. Paratypes ( ZIN): same locality and collector, 39.II.2019: 2 L-S-I ♂, 3 L-S ♂, 1 L-S-I ♀, 1 L-S ♀, L/S ♂, 19 larvae .

Descriptions. Larva. CUTICULAR COLORATION. Head, thorax, legs and abdomen nearly uniformly brown ( Figs 45–46 ). Caudalii lighter, brown proximally and near apex, with posterior margin of each 4th segment brown ( Fig. 43 ).

HYPODERMAL COLORATION. Mature larvae of both sexes with large lateral dark markings on abdominal terga, as in winged stages (as in Figs 67–68 , 73–75 ).

SHAPE AND SETATION. Labrum as in other Oculogaster ( Figs 49–50 ). Mandibles with incisor and kinetodontium fused more than to middle, with ventral denticle well-developed; incisor of right mandible with 2nd denticle shortest; right prostheca apically with 2–6 short parallel processes ( Figs 51–52 ). Maxillary palp 2-segmented ( Fig. 54 ). Labium with glossae and paraglossae of subequal size, palp with median angle moderately projected ( Fig. 55–54 ). Femora with very small spine-like setae on outer and inner sides, with 2 spine-like apical setae located in plane of leg; apical setae pointed or blunt, larger than other spine-like setae or equal to them (as in Fig. 17 ). Claws moderately long, with two rows of denticles, minute in proximal part and larger more distally, exceeding mid-length of claw ( Fig. 66 ). Hind protoptera completely absent. 1–4 lateral spines on posterior part of abdominal segment IX only ( Fig. 47 ). Posterolateral spines present on segments VI–IX, being minute on most anterior of these 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, shorter on anterior terga and longer on posterior terga ( Fig. 47 ); on tergum IX row of denticles interrupted medially, behind pair of submedian setae ( Fig. 47 ). Abdominal terga with short scales in wide semilunar or W-shaped non-opercula-bearing sockets, with sparse simple fine setae; one pair of bifurcate setae ( Fig. 48 ) near midlength of each tergum VIII–IX and one pair of bifurcate setae near posterior margin of each tergum VII and IX (as in Fig. 3 ). Posterior margins of abdominal sterna I–IV smooth, posterior margin of sternum 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. Tergalius I with costal rib very short and lacking denticles; costal rib on tergalii II–VII longer, either without denticles or with few small denticles on apex; dorsal lamella present either on tergalii I–V, or II–IV ( Figs 57–65 ). Cerci with especially long and slender distal portions lacking swimming setae and lateral spines ( Fig. 43 ). In distal part of cercus (proximad of slender setae-less distal portion) spine on lateral side of each segment subequal or slightly longer than next segment ( Fig. 43 ).

Subimago. CUTICULAR COLORATION. Head colorless. Pronotum with brown and colorless areas. Mesonotum brown with sutures darker brown, with large colorless areas occupying anterior part of submedioscutum and posterior scutal protuberance ( Fig. 70 ). Thoracic pleura mostly colorless, with some sclerites brown ( Fig. 69 ). Legs nearly colorless, with base of tibia brown, sometimes brownish stripes on femur. Abdomen very light brownish with sigilla colorless. Caudalii light brownish.

TEXTURE. On fore leg of male and female, 1st tarsal segment covered partly with microtrichia (as in tibia), partly with pointed microlepides; all other tarsal segments entirely covered with pointed microlepides ( Figs 7677 ).

Imago, male ( Figs 67–68 ). Head ocher with brown. Antenna pale ocher, joining of scapus and pedicellus brown. Turbinate eyes widened apically; facetted surface and dorsal part of stem light yellow, ventral part of stem brown. Thorax brown, with sterna lighter yellowish, pleura with longitudinal white and darker brown bands. Legs light yellow. In paratype, ratio femur / tibia / tarsal segments (mm) on fore leg 1.10: 1.55: 0.05: 0.72: 0.60: 0.30: 0.17; on middle and hind leg 0.92: 0.88: 0.30: 0.13: 0.05: 0.15. Middle and hind legs normally with 2 apical spines: on 1st+2nd and on primary 3rd tarsomeres (as in Fig. 77 ) (among specimens examined, only in holotype one of these spines lacking on some legs). Wing with membrane colorless, veins ocher; subcostal vein proximad of costal brace colored with brown. Pterostigma with one oblique cross vein; besides it, costal field with very slender cross vein belonging to middle cord of cross veins. Marginal intercalaries present in most of interspaces, both behind convex and concave longitudinal veins. Hind wing absent. Abdominal terga mostly brown; terga II–VI with lateral areas dark brown, median area lighter, with pair of light spots adjacent to anterior margin, light submedian sigilla and unpaired light spot adjacent to posterior margin; tergum VII dark brown with pair of light spots adjacent to anterior margin and light submedian sigilla; terga VIII–X dark brown with light submedian sigilla. Abdominal sterna light ocher, with pair of longitudinal lateral brown stripes. Gonostyli pale ocher, penis brown. Median projection of penis semicircular ( Fig. 71 ). Cerci whitish, with brown apex of each segment or every 2nd segment.

Imago, female ( Figs 73–76 ). Head moderately wide, distance between eyes subequal to eye length; eyes only slightly elevated above head surface. Head ocher, with reddish brown and white stripes. Pronotum ocher, with small brown spots. Mesonotum ocher, bordered with reddish-brown and white stripes. Thoracic pleura ocher with wide white and brown longitudinal bands. Sterna and legs light yellow. Fore leg without apical spine on 2nd tarsomere, with single apical spine on primary 3rd tarsomere ( Fig. 76 ); middle and hind legs each with 2 spines ( Fig. 77 ) (as in male – see above). Wings as in male (see above). Abdominal terga with peculiar contrasting ornament gradually changing from tergum II to tergum IX, including dark reddish-brown lateral areas, medial ocher area and paired white spots; terga VIII–IX with median reddish-brownish stripe; tergum X reddish-brownish ( Fig. 73, 75 ). Abdominal sterna ocher, with pair of longitudinal lateral reddish-brown stripes ( Fig. 74 ). Cerci as in male (see above) ( Fig. 73–74 ).

Egg. Without rigid chorion (viviparity).

Dimension. Fore wing length of male 4–5 mm, female 6 mm.

Larval habitat. Larvae were collected in a small stream running in dark forest; just below the waterfall, this stream represent a chain of pools bordered by rocks, among which the first pool (into which the waterfall falls) is large, and downstream pools are smaller; all larvae of P. (O.) niger sp. n. were collected in a single pool, which is the 3rd from the waterfall; in spite of intensive collecting, in other places of this stream such larvae were not found.

Comparison. Larva of the new species P. (O.) niger sp. n. differs from P. (O.) barnardi sp. n. and P. (O.) cylindroculum by the uniform brown coloration of abdominal terga, longer rows of denticles on claws and by the presence of lateral spines on abdominal segment IX only. Thin terminal portions of cerci lacking swimming setae and spines, in P. (O.) niger sp. n. are usually longer than in other species ( Fig. 43 ). Imago and subimago of P. (O.) niger sp. n. differs from P. (O.) barnardi sp. n. and P. (O.) cylindroculum by the presence of 2 apical spines on middle and hind tarsi ( Fig. 77 ). Winged stages of male and female differ from other species by more extensive and uniform brown hypodermal pigmentation of abdominal terga.

Figures

FIGURES 43–48. Larval exuviae of Procloeon (Oculogaster) niger sp. n. 43–44, caudalii; 45, abdomen; 46, half of pronotum and mesonotum; 47, male uromeres IX–X; 48, fragment of abdominal tergum VIII (arrow shows long bifurcate seta near midlength) (43–46, holotype).

FIGURES 49–56. Larva of Procloeon (Oculogaster) niger sp. n. (holotype): 49–50, labrum with focus on ventral and dorsal sides; 51–52, left and right mandibles; 53–54, maxilla (ds1–ds3, dentisetae); 55–56, labium with focus on dorsal and ventral sides.

FIGURES 57–66. Larvae of Procloeon (Oculogaster) niger sp. n. 57–62, tergalii I–III and V–VII; 63–65, tergalii I, IV and VII of other specimens (64–65, holotype); 66, claw.

FIGURES 67–70. Male Procloeon (Oculogaster) niger sp. n. 67–68, male imagines; 69, subimaginal exuviae of postsubalar sclerite; 70, subimaginal exuviae of mesonotum (67, 69, holotype).

FIGURES 71–72. Male Procloeon (Oculogaster) niger sp. n. 71, genitalia of imago (penis dotted; gonostylar muscle not shown at right, penial muscles not shown at left); 72, their subimaginal exuviae.

FIGURES 73–77. Female Procloeon (Oculogaster) niger sp. n. 73–74, imago; 75, imaginal abdomen; 76–77, subimaginal exuviae of fore and middle tarsi (arrows show spines; 1st–5th, initial tarsomeres).

FIGURES 17–18. Larva of Procloeon (Oculogaster) barnardi sp. n., middle leg. 17, apex of femur and base of tibia, anterior view (patella-tibial suture and bases of fine setae are visible as light markings on darker background); 18, more distal part of tibia, posterior view (with continuation of patella-tibial suture visible as light line).

FIGURES 1–7. Procloeon (Oculogaster) barnardi sp. n. 1–6, male larva ready to moult to subimago: 1–2, larval cuticle detached from thorax and abdomen; 3, fragment of abdomen (arrows show bases of bifurcate setae similar to Fig. 48); 4, intact specimen (IV–IX, abdominal segments); 5, extracted subimaginal thorax; 6, extracted subimaginal abdomen; 7, same, female.