Procloeon (Securiops) falcatum ( Crass 1947 ) Kluge, 2023

Kluge, Nikita J., 2023, Redescription of the subgenus Securiops Jacobus, McCafferty & Gattolliat 2006 (Ephemeroptera, Baetidae, Procloeon Bengtsson 1915), Zootaxa 5343 (3), pp. 243-272 : 252-255

Procloeon (Securiops) falcatum ( Crass 1947) comb. n.

( Figs 1–7 , 25–65 )

Centroptilum falcatum Crass 1947: 80 (J & ♀ imago).

Afroptilum (Afroptilum) falcatum: Gillies 1990: 99 .

Cheleocloeon falcatum: Lugo-Ortiz & McCafferty 1998: 379 .

Potamocloeon macafertiorum: Jacobus & McCafferty 2005: 474 (larva, partim).

Material examined. SOUTH AFRICA, Western Cape Province: Cape Winelands District, Jonkershoek Valley, Eerste River upstream Stellenbosch , Swiss Club (5 km SE Stellenbosch), 33°57′30″S, 18°55′E, 18–22.I and 8– 12.II.2019, coll. N. Kluge & L. Sheyko: 1 L-SJ, 1 L/SJ, 2 larvae; the same locality and collectors, 8–11.II.2019: 2 larvae .

Descriptions

Larva. CUTICULAR COLORATION. Cuticle of anterior part of head nearly colorless, occipit light brownish. Pronotum, mesonotum and metanotum with composite pattern of colorless, light brown and dark brown areas ( Fig. 27 ). Fore protopteron with colorless base and dark brown striation on convex veins iRSa, iRSa 2, iRS and on distal portions of convex veins MA 2 and iMP ( Fig. 30 ). Hind protopteron brown basally, colorless at most part ( Fig. 29 ). Mesothoracic and metathoracic pleura brown ( Fig. 29 ), prothoracic pleura and all thoracic sterna colorless. Legs mostly colorless, with brownish darkening in distal part of femur, proximal part of tibia and distal part of tarsus ( Fig. 28 ). Abdominal terga with composite pattern of colorless, light brown and dark brown areas, with brown coloration most expressed on tergum VI ( Fig. 26 ); terga IV and VII without medial longitudinal stripe (in contrast to P. (S.) macafertiorum ). Abdominal sterna either nearly entirely colorless, or with contrasting brown longitudinal sublateral stripes ( Fig. 25 ). Caudalii nearly colorless, with brown bands on each 4th segment (as in Fig. 66 ).

HYPODERMAL COLORATION. Not expressed; shortly before molt to subimago, subimaginal coloration becomes visible through larval cuticle (as in Figs 59–63 ).

SHAPE AND SETATION. Mouthparts characteristic for Securiops (see above) ( Figs 31–46 ). Paraglossae nearly oval, with inner margin either evenly convex ( Figs 42–43 ), or slightly concave in distal half (left side on Fig. 41 ). On dorsal side of glossae, cuticle with transverse light brown sclerite just proximad of transverse setal row ( Fig. 46 ); remainder cuticle of labium colorless. Distal segment of labial palp without row of stout setae, with several stout setae near outer-distal and inner-distal corners ( Fig. 44 ).

Legs ( Figs 47–50 ): Femur, tibia and tarsus with rather small, stout, pointed, spine-like setae. On femur, all these spine-like setae equally small, located mostly on outer and inner sides not forming regular rows ( Fig. 47 ). On tibia and tarsus, these spine-like setae irregularly dispersed on all sides ( Fig. 49 ); only in distal part of tarsus forming rather regular longitudinal row. Claws characteristic for Securiops (see above) ( Fig. 50 ).

Lateral spines present on abdominal segments IV–IX, varying from 2 to 8 spines on one side ( Figs 25–26 ). Small posterolateral spines present on segments II–VII.

Posterior margin of abdominal tergum I smooth, without denticles; posterior margins of terga II–X with heavily sclerotized, conic, sharply pointed, spine-like denticles separated by spaces wider than denticle width ( Figs 51–56 ); on tergum IX row of denticles interrupted medially, behind pair of submedian setae ( Figs 51 , 56 ); projected portion of tergum X row with pair of larger denticles by sides and straight row of smaller denticles between them ( Figs 51–52 ).

Posterior margins of abdominal sterna I–III smooth, without denticles; posterior margins of sterna IV–IX with spine-like pointed denticles, smaller and denser than denticles on terga ( Fig. 57 ). Paraproct with spine-like denticles larger than denticles on sterna ( Fig. 52 ).

Abdominal terga, sterna and paraprocts with oval scales in wide semilunar non-opercula-bearing sockets. Terga I–II without scales, with numerous small, pointed denticles ( Fig. 53 ); tergum III with few scales and many denticles ( Fig. 54 ); terga IV–X with numerous scales and less prominent denticles or with blunt transverse ridges instead of denticles ( Figs 55–56 ). Sterna I–III without scales; sternum IV with few scales; sterna V–IX with numerous scales ( Fig. 57 ).

Besides scales, abdominal terga and sterna with ring-like sensilla and fine setae. Fine setae vary from simple to bifid, from small to long, located sparsely and irregularly, not forming regular rows; each tergum VII–IX and sternum II–VIII with pair of long, bifurcate setae ( Fig. 58 ).

Tergalii without denticles on costal ribs; dorsal lamella roundish, present on tergalii I–VI and absent on tergalius VII. Tergalius I shorter than others, widened, with anal margin sharply convex and costal margin concave ( Fig. 1 ). Tergalii II–VI gradually changing from this shape to oval shape of tergalius VI ( Figs 2–6 ). Tergalius VII with costal margin sharply convex ( Fig. 7 ).

Caudalii characteristic for Procloeon /g1 and Cloeon /fg1 (see above). Spines on lateral side of cercus gradually change from shorter in proximal part of cercus to longer in its distal part; in distal part of cercus, spine on lateral side of each segment twice longer than next segment (as in Figs 71–72 ).

Subimago. CUTICULAR COLORATION. Cuticle of thorax mostly colorless, only selected areas of mesonotum and thoracic pleura contrastingly dark brown (as in Figs 84–85 ).

TEXTURE. On legs of all pairs, all tarsal segments covered with pointed microlepides (as in Figs 71–72 ).

Imago, male. Not examined; described by Crass (1947). Judging by hypodermal coloration of the male subimago reared from larva, and by subimaginal tissues in the mature male larva, fore femur has brown spot at proximal part ( Fig. 63 ) and abdominal terga have variable brown markings, most extensive either on tergum IV ( Fig. 61 ), or on terga IV and VII ( Fig. 59 ). Hind wing with hooked costal process and with two veins ( Fig. 64 ), wider than in P. (S.) macafertiorum . Middle and hind legs with tarsus longer than tibia, with two apical spines on initial 2nd and 3rd tarsomeres (actual 1st and 2nd tarsomeres) (as in Fig. 87 ). Judging by subimaginal genitalia, penial bridge forms wide, semicircular projection ( Fig. 62 ).

Imago, female. Undescribed; reported by Crass (1947).

Egg. Unknown.

Dimension. Specimen examined with fore wing length 5.5 mm; according to Crass (1947), fore wing length 6–8.5 mm.

Notes. Originally ( Crass 1947), the species under the name Centroptilum falcatum was described based on imagines collected in South Africa. Lugo-Ortiz & McCafferty (1998) placed falcatum [ Centroptilum ] in the genus Cheleocloeon Wuillot & Gillies 1993 , because they regarded its imago to be similar to another South-African species, which was originally described under the name Centroptilum excisum Barnard 1932 and currently placed in the genus Cheleocloeon . They wrote: ́The only difference between the two species is the presence of hind wings in female adults of C. falcatum ». Actually, male imagines of these species well differ one from another by genital structure. Till now, genitalia of Cheleocloeon excisum have not been described, but our material (imagines reared from larvae in South Africa) reveals that they have a structure typical for Cheleocloeon , with hook-like movable gonovectes and non-sclerotized penial bridge ( Kluge 2016a) ( Fig. 145 ). In contrast to this, genitalia of falcatum [ Centroptilum ] were originally figured as having prominent semicircular penial bridge ( Fig. 65 ; Crass 1947: fig. 20b), which is characteristic for Cloeon /g1, but not for Cheleocloeon . Judging by this figure, genitalia of falcatum [ Centroptilum ] are similar to P. (S.) macafertiorum : both have unistyligers widely separated and gradually narrowing distally ( Fig. 90 ), while in Cheleocloeon excisum unistyligers are brought together, and articulation of the gonostylus with the unistyliger has composite structure ( Fig. 145 ).

Figures

FIGURES 1–24. Right tergalii of Securiops with dorsal lamella turned out. 1–7, Procloeon (Securiops) falcatum, tergalii I–VII; 8–17, two individuals of P. (S.) macafertiorum: 8–11, tergalii I–II and V–VII; 12–16, tergalii I–V; 17, the same individual, margins of abdominal segments VII–IX with tergalius VII in natural position; 18–24, P. (S.) primasia, tergalii I–VII.

FIGURES 25–30. Procloeon (Securiops) falcatum. 25–28, larval exuviae (with same magnification): 25, abdominal sterna; 26, abdominal terga; 27, half of pronotum and mesonotum; 28, fore leg; 29, exuviae of metanotum with hind protoptera, left metapleuron and 1st abdominal tergum, enlarged; 30, fore protopteron, to show correspondence between cuticular coloration and veins visible inside.

FIGURES 31–39. Procloeon (Securiops) falcatum, larval mouthparts. 31, apex of labrum, ventral view; 32, labrum, dorsal view; 33, apex of labrum, enlarged; 34–35, left and right mandibles; 36, maxilla; 37–38, apex of maxilla with focus on ventral and dorsal sides; 39, hypopharynx with superlinguae.Abbreviations: can, maxillary canines; ds1, ds2, ds3, 1st–3rd dentisetae,

FIGURES 40–46. Procloeon (Securiops) falcatum, labium. 40, integral labium; 41–46, parts of exuviae: 41, glossae and paraglossae, ventral view; 42, half of labium of another individual (ventral setae of glossae directed distally); 43, the same individual, with ventral setae of glossae directed proximally; 44, distal segments of labial palp; 45–46, enlarged glossae in ventral and dorsal view (ventral setae directed distally). Abbreviations: m2-3, muscle going from 2nd palpomere to base of 3rd palpomere; pm1, pm2, pm3, 1st–3rd palpomeres; s.d, dorsal setae of glossae; s.v, ventral setae of glossa.

FIGURES 47–52. Procloeon (Securiops) falcatum, larva. 47, articulation of femur and tibia of fore leg, dorsal view; 48, the same, compressed to show junction of patella-tibial suture with row of fine hairs; 49, fragment of tarsus; 50, claw; 51, abdominal tergum X and margin of tergum IX; 52, abdominal tergum X and paraprocts.

FIGURES 53–58. Procloeon (Securiops) falcatum, exuviae of larval abdomen. 53–56, terga II, III, IV and IX; 57, sternum IV; 58, constant bifurcate seta on sublateral part of sternum VIII.

FIGURES 59–65. Procloeon (Securiops) falcatum. 59–60, parts of male subimago extracted from larva: 59, abdomen; 60, genitalia; 61–64, young male subimago: 61, abdomen; 62, genitalia; 63, fore femur; 64, hind wing (partly crumpled); 65, genitalia of male imago (after Crass 1947). Abbreviations: gs1, gs2, gs3, 1st–3rd segments of gonostylus; pb, median projection of penial bridge; usg, unistyliger.

FIGURES 66–69. Larvae of Procloeon (Securiops) macafertiorum. 66–68, larval exuviae (with same magnification): 66, abdominal terga and sterna; 67, thoracic sterna, pleura, halves of metanotum with hind protoptera and right legs (arrows show hind protoptera); 68, half of pronotum and mesonotum; 69, last instar male larva.

FIGURES 70–76. Procloeon (Securiops) macafertiorum. 70, subimaginal exuviae: apex of tibia and base of tarsus of fore leg of male; 71–76, larval exuviae: 71, caudalii; 72, fragment of cercus; 73, fragment of fore tarsus; 74, abdominal tergum IV; 75, abdominal sternum V; 76, abdominal tergum X, paraproct and margin of tergum IX.

FIGURES 77–87. Procloeon (Securiops) macafertiorum. 77, 78, male imagines; 79, female imago; 80–87, parts of male imago and subimago reared from larva: 80–81, head and thorax; 82, abdomen; 83, hind wing; 84, subimaginal exuviae of thoracic pleura; 85, subimaginal exuviae of half of mesonotum; 86–87, fore and hind legs. Abbreviations: cx2, cx3, coxae of middle and hind legs; lpnc, lateropostnotal crest; mtpl, pleurite of metathorax; pls, pleural suture; psa, postsubalar sclerite.

FIGURES 143–145. 143–144, eggs of Procloeon (Securiops) primasia. 145, male imaginal genitalia of Cheleocloeon excisum (Barnard 1932), reared from larva in Eerste river 9.II.2019 by N. Kluge and L. Sheyko [the same locality as for P. (S.) falcatum]. Abbreviation: mp, micropyle.

FIGURES 88–91. Procloeon (Securiops) macafertiorum. 88, genitalia of male imago reared from larva; 89, its subimaginal exuviae; 90, genitalia of another specimen, ventral view; 91, the same, with focus on penis.