Mecolenus wahlbergi Schoenherr, 1847

Wanat, Marek & Procheş, Şerban, 2021, Contribution to morphology, biology and distribution of Mecolenus wahlbergi Schoenherr, 1847, a relict African apionine weevil (Coleoptera: Brentidae: Apioninae), Zootaxa 5067 (1), pp. 40-54 : 42-50

Mecolenus wahlbergi Schoenherr, 1847

( Figs. 1–57 )

Mecolenus wahlbergi Schoenherr, 1847: 7

Material examined. South Africa. KwaZulu Natal : Malvern [Durban], 1 ♀ ( BMNH) ; 29.885833°S / 30.925555°E, 9 X 1902, 3 ♂♂, leg.? ( DNSM: COL 006987 , COL 006988 , COL 006989 ) ; Durban , 29.98°S / 30.96°E, 2 ♂♂ 2 ♀♀ [originally all mounted on single card, re-mounted to individual cards and labelled: ‘ex. for SEM, M. Wanat, 18.09.2014 /5-8’] ( ISAM: COL-A068549 ) ; Eshowe , 28.887222°S / 31.470833°E, 1 XI 1943, 1 ♀ (teneral specimen), leg. B. Marley ( DNSM: COL 006994 ) ; Saint Lucia Lake , 27.966666°S / 32.5°E, 1 VII 1944, 1 ♀, leg. B. Marley ( DNSM: COL 006990 ) ; Amanzimtoti South Coast , 30.05°S / 30.883333°E, 25 II 1945, 1 ♂, leg. B. Marley ( DNSM: COL 006992 ) ; Maclear [???], 12 III 1944, 1 ♂ 1 ♀, leg. B. Marley ( DNSM: COL 006991 , COL 006993 ) ; Umtamvuna ( Pont ), Kingfisher circuit trail, 31.064°S / 30.175°E, 10–15 m alt., 2 XII 2019, 1 ♂ 1 ♀, leg. M. Wanat ( MWC) . Eastern Cape : Port St. John [s], Pondoland, 1 ♂ 1 ♀ ( BMNH) ; Z.A.84, Port St. John [s] D., Nxolveni Forest [= Silaka Reserve?], XII 1961, humus, 1 ♂ ( TMSA) ; 75 km E of Umtata - 15 km W of Port St. Johns , 30 m alt. [Ndwalane vic., 31.6°S / 29.46°E], 11 I 2010, 1 ♀, leg. A. Kudrna ( CGC) .

Remark. It is unclear if ‘Maclear’ on the labels of two specimens refers to the town in Eastern Cape Province [31.08°S / 28.37°E] or to an unidentified area in Durban called ‘Maclear Bush’, as it was catalogued in DNSM.

Redescription. Body length 4.6–6.0 mm, width 1.9–2.5 mm.

Integument uniformly dark brown to piceous-black, both on dorsal and ventral side of body seemingly naked, vestiture generally reduced to microscopic setae not surpassing their basal punctures and visible only under high magnification ( Figs 1–4 ).

Rostrum subcylindrical, slightly narrowed at antennal insertion ( Fig. 2 ), in profile straight on most length and curved apicad from antennal pits ( Fig. 8 ); prorostrum declining apicad, smooth, around with dense small punctures of one ommatidium size; metarostrum rough, lacking sulci and keels, microreticulate, with dense polygonal punctures, on sides often confluent into oblique irregular furrows; antennal pits long-oval; scrobes lateroventral, sulciform, with sharp outer margins, occupying entire metarostrum venter and vanishing before head, separated by wedge-like flat septum covered with coarse punctures bearing microscopic setae ( Fig. 9 ).

Mouthparts: labral part of rostrum as a broad rectangular projection of epistomal margin, slightly raised and visible as a small tooth above mandibles in rostrum profile, epistomal pits and setae absent; maxillary palpifer with 2 setae; maxillary palpi 2-segmented, basal segment with single seta; labium with a pair of lateromedial setae, labial palps small, with 2–3 long setae; ligula with long setation ( Fig. 10 )

Antennae inserted subapically, distinct sexually in length and segmental proportions of distal antennomeres excepting subisodiametric 7 th funicular segment, with short and protruding dark setation, denser and shorter on the club; scape 5.6–5.8, 2 nd funicular segment 3.3–4.0 × as long as wide; club compact, evidently pseudotetramerous, longer than 5 distal funicular segments combined ( Figs 8, 11 ).

Head narrow and elongate, rectangular in dorsal view, subconical in profile ( Fig. 8 ); eyes inconspicuous, regularly convex, barely shorter than rostrum width at base; epifrons between eyes 0.6–0.7 × as wide as rostrum at base, with arched shiny rib along each eye margin, in middle scale-like microsculptured and impunctate ( Fig. 2 ); vertex flat, irregularly roughly punctate; temples with coarse vertical wrinkles; no longer setae around eyes ( Fig. 8 ) gular area between eyes nearly flat, impunctate, posteriorly with 2–3 coarse transverse wrinkles ( Fig. 9 ).

Pronotum 0.85–0.90 × as long as wide, widest well before mid-length, strongly constricted subapically and rounded, not constricted at base ( Fig. 3 ); disc emarginate anteriorly, straight basally, evenly convex, densely and irregularly tuberculate-punctate, punctures shallow funnel-like, with convex interspaces elevated to form irregular elongate-sinuate tubercles ( Figs. 4 , 12 ); prescutellar fovea taking most of disc length, well margined; basal flange and subbasal line absent, pronotal corners slightly obtuse-angled ( Fig. 3 ); notosternal suture ending in a deep pit; pronotal sides in front with several irregular superficial wrinkles close to anterior and posterior margins, lacking posterior groove; prosternum about 3 × narrower than hypomeron, declining posterad, prosternellum separated from hypomeron by fine suture, small, rhombic, convex; procoxal cavities large, contiguous, on bottom with a foramen taking about 2/3 of their diameter, posteriorly with a narrow complete raised rim; hypomeron with superficial median suture, flat and impunctate, marginal fringe of setae vestigial ( Fig. 13 ).

Elytra pyriform, regularly convex, 1.75–1.90 as wide and 3.0–3.2 × as long as pronotum; elytral suture apically straight and simple, i.e. without pocket-like lock ( Figs. 20, 21 ), basal lock of multituberculate type, with a small pit followed by two large elongate tubercles on the left elytron ( Fig. 18 ), and small tubercle followed by two elongate holes on the right one ( Fig. 19 ); elytron base roundly projecting and raised to a distinct rim between scutellar shield and humerus, with five striae present, stria 1 only slightly shortened, approximating the level of scutellum; striae catenulate-punctate, shallow, with small deep punctures separated with 2–3 × longer depressed interspaces each bearing a field with several pores and single minute seta to be seen only under scanning microscope ( Fig. 14 ); apically only the junction of striae 1+9 evident, which should be coded (1+9)+10 due to presence of subhumeral remain of stria 10 ( Fig. 15 ) and lacking its apical separate remain; stria 8 free apically, striae 2 and 7 corresponding in their courses but separated by a narrowly extended connection of intervals 3 and 7, inner striae usually joining 3+4, 5+6, or the pattern is disturbed by merged connections ( Fig. 16 ); intervals in middle of elytral disc ca. 1.5 × as wide as striae, asymmetrically elevated, with rib-like raised outer margin, surface of the interval even, shagreened and matt, with a row of microscopic sensory fields similar as in the striae ( Fig. 17 ), on the steep side outwards from rib with a regular row of small asperities positioned exactly opposite to strial punctures, on intervals 5–9 with additional analogously ordered and positioned asperities on the inner side of interval ( Fig. 16 ); specialized setae two distant in about middle of interval 7 and a close pair in apical 0.25 length of interval 9.

Wings functional, broadly melanized distally along radial and medial veins; radial window distinct, long and narrow; cubito-anal vein remnants paired, simple; main anal vein (3A in Zherikhin and Gratschev, 1995, 2A in Wanat, 2001, AAP in Fedorenko, 2009) straight, without spurs; subsequent 3A vein, short, straight; anal notch obsolescent ( Fig. 5 ).

Pterothorax. Scutellar shield small, glabrous, button-like ( Fig. 14 ). Mesoventrite at widely obtuse angle with collar, glabrous in middle, with several shallow punctures on sides; anapleural sutures visible, arched; mesepimeral suture as sharply edged sulcus, shallow, with vanishing punctures. Mesepimera impunctate, Mesocoxal cavities shortly oval, on metaventrite bordered with a complete, narrow but high rim, narrowly separated by a complete septum consisting largely of mesosternal process 2.5–3.0 × as long as higly raised metaventral process Metaventrite less than 1.2 × longer from mesocoxal cavities, along metacoxal cavities deeply impressed to form a complete metakatepisternal fovea closed laterally with joined folds of cuticle ( Fig. 22 ). Metanepisternum with a broad impunctate median sulcus; metepimeron small, markedly elongate ( Fig. 15 ).

Legs: fore pair markedly longer than remaining two, with swollen femora. Procoxae pear-shaped, flattened on outer side and thus with a vertical blunt edge running from the anterior margin of trochanter socket towards coxal base ( Fig. 4 ), with the narrowed apices curved outwards and separated by transverse rim in middle of inner side of coxa ( Fig. 13 ); all coxae apically with a distinct tooth-like condyle limiting rotation of trochanter ( Figs. 13 , 22 ); metacoxae with a complete and deep median transverse sulcus ( Fig. 22 ).Trochanters securiform, 1.5–1.6 × as wide as long. Femora impunctate, with sparse microscopic setae based on minute asperities, finely transversely wrinkled on dorsal side; the asperities on ventral side enlarged to form cylindrical tubercles, obtuse and bearing a minute seta apically ( Figs. 23, 24 ); tubercles higher towards distal end of femur, on fore femora numerous in multiplied rows, on mid- and hind femora a few in a single row ( Fig. 25 ); the knee parts of femora coarsely furrowed. Tibiae with complete sharp edge along outer and inner side, anteriorly with additional carina parallel to outer edge - incomplete on protibia, complete on meso- and metatibia, the latter two having on apices distinctly extended upwards tarsal groove surrounded by a complete comb of long outwards and much shorter inwardly brownish setae, without paired distinct setae ( Fig. 25 ); protibia without spines along inner edge. Tarsi with dense yellowish adhesive sole, short and small, of the same peculiar shape on all legs and in both sexes ( Fig. 29 ). Protarsus 1.8 × as long as wide; tarsomere 1 gently emarginate, about as long as wide; tarsomere 2 markedly emarginate and transverse, about 0.6 as long as wide; tarsomere 3 enlarged, 0.85–0.95 as long as wide, only slightly shorter than combined tarsomeres 1+2; onychium shorter than lobes of tarsomere 3, 2.20–2.35 × longer than wide, apically with a pair of straight-forward projecting special long setae, truncate, three-angled in cross-section and with median canal; claws robust, with large and broad, lamelliform teeth ( Figs 27, 28 ).

Abdomen: ventrites 1+2 combined not less than 4 × as long as ventrites 3+4, finely punctate, finely transversely wrinkled on sides, sparsely and superficially punctate, punctures setiferous, much smaller in smooth middle of ventrites; ventrites 3–5 convex, first two more densely microreticulate; ventrite 5 with dense, partly confluent transversely punctuation, and more distinct appressed setation. Rectum very broad, with a sclerotized ring close to anus, at the level of opening of common oviduct to vagina ( Figs. 50, 51 ).

Male. Rostrum 2.9–3.4 × as long as wide, longer than pronotum (ratio 1.04–1.11); metarostrum 2.30–2.87 as long as eye. Antennae 0.65–0.75 as long as elytra and 2.2–2.3 as pronotum, inserted at apical 0.24–0.29 of rostrum; scape 1.4–1.7 × longer than width of rostrum at antennal insertion; length/width of funicular segments: 1 st 2.35– 2.50, 3 rd 2.45–2.70, 4 th 2.30–2.45, 5 th 1.55–1.70, 6 th 1.4; club 5.1–6.3 as long as wide, with third segment 1.3 × longer than combined segments 1+2, narrowly conical distad from distinct median constriction ( Fig. 8 ). Head 1.39–1.52 as long as wide; eye taking 0.34–0.39 of total head length; vertex roughly punctate on a distance 1.4–1.5 × longer than eye. Fore legs extraordinarily long; profemur 3.65–3.90 as long as high (spines not included), 1.88–1.96 as high as width of rostrum at antennal insertion, thickest in about basal third, ventrally with a triple confused row of spine-like asperities ( Fig. 23 ); protibia long and strongly curved inwards, 8–10 × longer than its width and 2.00–2.25 × longer than pronotum, with modified, obliquely furrowed falcate apical part ending in form of a minute spine surrounded by divided tuft of short apical setae ( Figs 26, 27 ); mid- and hind tibiae with vestigial mucro not projecting from a continuous row of short apical setae ( Figs. 30, 31 ). Abdominal ventrite 5 broadly truncate apically, 3.3–3.4 as wide as long ( Fig. 6 ).

Tergite VII subrectangular, broadly truncate-emarginate, over 2.5 × wider than long, evenly sclerotized and setose in apical half-length ( Fig. 32 ); membrane of tergite VII without median invagination. Pygidium half-exposed, with deep transverse sulcus separating the two parts ( Fig. 34 ); exposed part rough, indefinitely punctate, with dense, fine, semirecumbent brown setae; anterior apodemes small; internal tongue-like process absent ( Fig. 33 ). Sternite VIII undivided, with very short lobes, evenly sclerotized, lacking apodemes and median carinae ( Fig. 40 ); membrane between sternites VIII and IX lacking additional sclerites. Spiculum gastrale Y-shaped, symmetrical, with apodeme 2.5 as long as fork ( Fig. 41 ). Tegmen with Y-shaped ventral part, apodeme 1.2–1.3 as long as the arms, narrow apically; tegminal plate 1.5–1.6 as long as wide, broadly connate to basal piece, not developed latero-ventrally, deeply and broadly divided into paired lobes ending with crescentic sclerotization bearing 8–10 long macrochaetae on its margin, lacking membranous apical extensions; fenestrae indefinitely margined, separate on each lobe and restricted to ventral layer of tegminal plate, here closed by narrow sclerotized link between apical sclerotizations and prostegium, broadly open laterally; dorsal layer of tegminal plate behind apical sclerotizations fully membranous, thus lacking postfenestral plate, with the membrane folding directly on the level of fenestrae; prostegium weakly projecting in middle, unclearly bifid, evenly weakly sclerotized ( Figs. 42, 43 ). Penis: apodemes about as long as penile body, flat, markedly dilated apically, long dichotomous basally, with broad connections with tectum and almost equally broad and not constricted with pedon ( Fig. 35 ); tectum ca. 0.75 × as long as pedon, broad, well sclerotized at least basally; pedon ca. 2.5 × as long as wide, parallel-sided with triangular apex, in profile straight and gently narrowing apicad, apical margin finely serrulate and dorsally foveolate ( Figs. 36, 37 ); endophallus large, laying mostly outside penile body and surpassing apodemal apices in repose, its membrane with dense transverse microplates in proximal half, most of the distal half occupied with a peculiar transfer apparatus consisting of two long sclerites firmly connected on the functionally apical end with a thin sclerotized bar ( Figs. 38, 39 ); endophallus ending with paired small membranous lobes; paired frena present, crescentic, laying at the level of pedon base in repose ( Fig. 37 ); entrance of ejaculatory duct (gonopore) dorsal, near the middle of transfer apparatus ( Fig. 39 ).

Female. Rostrum 2.7 × as long as wide, shorter than pronotum (ratio 0.95); metarostrum 1.95 as long as eye. Antennae less than half as long as elytra and less than 1.5 × as pronotum, inserted at apical third of rostrum; scape 1.15 × longer than width of rostrum at antennal insertion; length/width of funicular segments: 1 st 2.0, 3 rd 2.3, 4 th 1.5, 5 th 0.95, 6 th 1.05 club 3.4 as long as wide, with third segment as long as combined preceding two, obtuse apically ( Fig. 11 ). Head 1.2 × as long as wide; eye taking 0.42 of total head length; vertex roughly punctate on a distance equal to eye length. Fore legs shorter; profemur 2.9 × as long as high (spines not included), 1.8 as high as width of rostrum at antennal insertion, thickest in middle, ventrally with a double regular row of less numerous spine-like asperities, distal being distinctly longer than in male ( Fig. 24 ); protibia shorter and weaker curved inwards, less than 6 × longer than its width and 1.4 × longer than pronotum, with apical part obtuse, not distinctly falcate nor obliquely furrowed, with undivided expanded field of short apical setae ( Fig. 28 ); mid- and hind tibiae without mucro. Abdominal ventrite 5 almost semicircular, ca. 2.4 as wide as long ( Fig. 7 ).

Tergite VIII broadly trapeziform, over 2 × as wide as long, sclerotized and setose as in male ( Fig. 44 ). Tergite VIII subrectangular, over 2.5 as wide as long, divided to concealed microsetose and exposed punctate parts separated by sharp edge weakly emarginate in middle, and associated with a row of protruding setae ( Figs. 45–47 ). Spiculum ventrale with triangular sternal plate and straight apodeme ( Fig. 48 ). Gonocoxites broadly divergent in repose, small, simplified, lacking styli and setae, with strong median keel and semi-transparent plate with sensory pores in apical half ( Fig. 45 ). Sheath of ovipositor simply membranous, lacking microsetose areas. Bursa consisting of single small rounded lobe, receiving spermathecal duct ventrally near the opening of common oviduct ( Fig. 51 ). Spermatheca c-shaped, smooth, without prominences on a corpus, gland small, bulbous ( Fig. 49 ); duct membranous, thin, not longer than bursa.

Comparative notes. Mecolenus wahlbergi is one of the most characteristic apionine weevils in the world fauna, distinguishable immediately thanks to several unique characters, such as the bizarre fore legs with multiplied spinelike femoral tubercles, uniquely modified tarsi, with onychium shorter than enlarged tarsomere 3 and provided with paired projecting sensory setae, and peculiar structure of specifically the outer elytral intervals, with regularly disposed button-like asperities corresponding to strial punctures. It shares many relevant characters with the genus Apiomorphus , including the arrangement of elytral striae (only with Apiomorphus s. str.), pronotum tuberculate rather than punctate, sculpture of head, procoxae with transverse rim separating narrower apex and tooth-like coxal process limiting rotation of short and transverse trochanter, armed femora (though with true spines and not in all Apiomorphus species ), and in terminalia specifically with a very similar sternite VIII and endophallic transfer apparatus. Nevertheless, Apiomorphus is distinct from Mecolenus in several important characters, e.g., foveiform and lateral antennal scrobes, sub-basal instead of subapical position of antennae, numerous specialized setae present along all odd elytral intervals, unmodified tarsal onychium, membrane of tergite VII with a pouch-like invagination, pygidium with tongue-like internal process, or endophallus lacking frena. Considering their morphological distinctness, the two genera have been placed in separate tribes of their own by Wanat (2021).

Distribution. KwaZulu-Natal (from Lake Saint Lucia in the north-eastern part of the province to Umtamvuna River in the south), Eastern Cape (vicinity of Port St. Johns, not far from KwaZulu-Natal border) ( Fig. 57 ).

Biology. The two above listed specimens from Umtamvuna were collected one by one on a beating sheath, from a small group of 1–2 m tall young saplings of Broad-leaved Wild-quince Cryptocarya latifolia Sond. (Lauraceae) ( Fig. 53 ) growing under several older trees, one over 10 m tall ( Figs. 54, 56 ). The weevils were placed together alive in a plastic tube and provided with a leaf of the same tree, on which at least the male fed producing elongate holes after 2–3 hours ( Fig. 55 ). Similar holes situated along and close to leaf margin are seen on one leaf already observed on the collection tree in Fig. 53 .

Figures

FIGURE 57. Localities of Mecolenus wahlbergi in South Africa (circles; question mark refers to doubtful record from Maclear).

FIGURES 1–7. Mecolenus wahlbergi, male. Dorsal habitus (1); head with rostrum in dorsal view (2); prothorax in dorsal (3) and lateral (4) views; hind wing (5); SEM micrographs: abdominal ventrites 1-5 and exposed pygidium of male (6), abdominal ventrites 1-5 of female (7).

FIGURES 8–19. Mecolenus wahlbergi, SEM micrographs. Male, head with rostrum and antenna, lateral view (8). Female (9–11): head with rostrum, ventral view (9); mouthparts (10); antenna (11). Male prothorax, lateral view (12). Female prothorax and procoxae, ventral view (13). Female elytral base and sutellum (14). Male pterothorax and subhumeral elytral margin with separate 9th and 10th striae (15). Male apical part of elytron (16). Female, detail of inner basal elytral striae and intervals (17). Male postscutellar sutural lock of left (18) and right (19) elytron.

FIGURES 20–31. Mecolenus wahlbergi, SEM micrographs. Male (20–23): sutural apex of left (20) and right (21) elytron; pterothorax, ventro-lateral view (22); profemur (23). Female: profemur (24), metafemur (25). Apex of protibia (26–28): male no. 1 (26); male no. 2 (27); female (28). Female tarsus (29). Male: metatarsus and tibial apex (30), mucro of metatibia (31).

FIGURES 32–43. Mecolenus wahlbergi, male. Tergite VII (32). Pygidium in dorsal (33) and lateral (34) views. Penis (35–39): entire in dorsal view (35); pedon in dorsal (36) and lateral (37) views; exposed endophallus with sclerotized transfer apparatus in lateral (38) and dorsal (39) views. Sternite VIII (40). Spiculum gastrale (41). Tegminal plate and basal piece in dorsal view (42). Tegmen in lateral view (43).

FIGURES 44–52. Mecolenus wahlbergi, female (44–51). Tergite VII (44). Tergite VIII in postero-dorsal view and gonocoxites (45). Tergite VIII in dorsal (46) and lateral (47) views. Spiculum ventrale (48). Spermatheca (49). Telescoped tergites VII & VIII and rectum with sclerotized ring (50). Bursa receiving spermathecal duct and common oviduct, lateral view (51). Male rectum contents with numerous leaf hairs of Cryptocarya latifolia under compound microscope (52).

FIGURES 53–56. The site of Mecolenus wahlbergi in Umtamvuna with Cryptocarya latifolia: a group of tree saplings from which the weevil pair was collected (53, 54); leaf with submarginal feeding holes of Mecolenus (55); taller trees including Cryp- tocarya growing behind the saplings (56).