Madachironomus, Andersen, 2016

Andersen, Trond, 2016, MADACHIRONOMUS, A NEW GENUS OF TRIBE PSEUDOCHIRONOMINI (DIPTERA: CHIRONOMIDAE, CHIRONOMINAE) FROM MADAGASCAR Abstract, CHIRONOMUS Journal of Chironomidae Research 29 (29), pp. 15-26 : 16-17

Madachironomus new genus

http://zoobank.org/ 40BE526D-5658-4CEA-83C9- 186057B84F12

Type species: Madachironomus lakazana sp. n.

Other included species: Madachironomus rongaronga sp. n.

Etymology: The name of the new genus is a combination of the first two syllables from the place name Madagascar using the suffix - chironomus.

Generic diagnosis

The adults have the fore tibiae with one spurred comb, mid- and hind tibiae each with two separate, spurred combs; all combs subtriangular with rather steep flanks, the 1–2 pairs of teeth flanking the spur arising from the base of the latter and farther distally than the other comb teeth. The male has a strong, moderately long, nearly parallel-sided anal point with broadly rounded apex, without microtrichia except at base, and a digitiform, apically split median volsella with strong brush-like setae. The female has sternite VIII with a very dense posteromedial to posterolateral field of setae, a nearly straight gonocoxapodeme VIII, gonapophysis VIII with closely adjacent, indistinctly separable lobes, ovoid seminal capsules with nearly straight spermathecal ducts and labium with internal apodeme and spinose chaetulae on dorsomedial surfaces.

Generic description

Adult male

Antenna. With 13 flagellomeres, AR about 2.4.

Head. Frontal tubercles absent. Temporal setae consisting of inseparably intergrading verticals and postorbitals, briefly bi- to tri-serial near transition of eye to its dorsomedial extension. Eye bare; dorsomedial eye extension parallel-sided, about 2.5 times as wide as high, mostly of 5 facets per diagonal; interocular distance in frontal view about 3 times the apical width of the extension, slightly lower dorsally than ventrally. Clypeus with numerous setae arising over nearly entire surface. Palp 5-segmented, palpomere 3 with 2–3 sensilla clavata apically.

Thorax. Not projecting anterodorsally or arching overhead; scutal tubercle absent. Antepronotum visible in dorsal view, medially with relatively narrow but deep V-shaped notch, each lobe narrowest in mid-section; in lateral view with dorsal projection to anterior and with curved subsurface contour indicating the anteromedial excavation; with dorsal and ventrolateral semi-spinose, short setae. Acrostichals weak, numerous, paired or interspersed with small, light spots without alveoli or setae; setae short, semi-spinose, occurring from near antepronotum to almost as far posterior as dorsocentrals. Dorsocentrals weak, numerous, unito irregularly tri-serial, beginning above parapsidal suture, setae slightly longer than acrostichals. Prealars uniserial to bi-serial. Supraalars absent, exceptionally 1. Scutellum with numerous weak setae, bi- to tri-serial. Alveoli of all thoracic setae not surrounded by circles lighter in color than adjacent surfaces.

Wing. Costa weakly extended, ending proximal to wing apex. R 2+3 ending at one third of the distance between apices of R 1 and R 4+5. FCu slightly proximal to RM. Brachiolum with 2–3 setae; costal extension with few non-marginal setae; R 4+5 occasionally with single seta apically; other veins and membrane bare. Squama with numerous, partly bito tri-serial setae.

Legs. Fore tibia with single, dark comb, with central protruding long spur; mid- and hind tibia with two triangular combs, each with protruding central spur. Fore tarsal beard absent. Pseudospurs absent. Sensilla chaetica present in proximal 1/3 of ta 1 of mid- and hind leg. Pulvillus pad-like, ventrally covered with elongate trichia, broadly triangular, shorter than empodium, reaching beyond tip of fifth tarsomere to about mid-length of claw.

Hypopygium. Anal point tapering to apex that is tongue-shaped in dorsal view, subacute and slightly curving ventrad in lateral view, without microtrichia except at base. Tergite IX with several weak setae to each side of the base of anal point. Phallapodeme well developed, aedeagal lobe with narrow, curved oral projection. Transverse sternapodeme narrow, strongly arched, with low, rounded orolateral projections. Pars ventralis absent. Median volsella composed of elongate, digitiform main stem, split in apical 2/3, projecting posteromedially, densely covered with more or less subulate setae, and with cluster of additional, long subulate setae arising from gonocoxite next to proximal corner of volsella. Superior volsella distally sclerotized, darker than surrounding structures, projecting caudad, not reaching past anal point or distal end of gonocoxite, with broadly triangular base with 1–2 dorsolateral setae, and hooked apical part with few mesally directed setae, without microtrichia on dorsal surface. Inferior volsella broadly digitiform in dorsal view, with microtrichia and normal to strong setae along entire medial length, on distal-dorsal surface and less densely distolaterally; proximoventrally with globose, more membranous expansion. Gonocoxite with 4 ventromedial setae proximal and 3 distal to median volsella. Gonostylus weakly curved with bluntly rounded apex, with row of short, curved setae along inner margin.

Adult female

As male except antenna with 6 flagellomeres; AR about 0.6; flagellomeres 1–5 each with submedial whorl of 3–5 strong setae and with subapical ring of 2–4 sensilla chaetica; flagellomere 6 with 15–20 sensilla chaetica in apical 3/4. Dorsomedial eye extension less distinct than in male, about 1.2 times as wide as high, mostly of 5–6 facets per diagonal; eyes separated by more than three times the width of the eye extension. Wing veins darker brown than in male, with dark spot along crossvein RM and radial fork; membrane brown with stronger shading along veins. Wing vein R 2+3 ending about half-way between apices of R 1 and R 4+5.

Abdomen. Tergites I, II, IV–VIII with successively increasing numbers of widely scattered, relatively short but strong setae arising in light-colored circles; tergite III with setae mostly concentrated anteriorly and posteriorly and few setae in between. Paratergites IV (except anteriorly) –VII with conspicuous longitudinal setation. Sternites II–V with (postero)lateral longitudinal rows or patches of setae, sternites VI–VII with these patches spreading to medial and anterior; in addition, sternites VI– VII with marginal rows of setae paralleling those on paratergites; sternite VII with posteromedial triangular field of more densely set setae.

Genitalia. Sternite VIII with very dense posteromedial to posterolateral field of setae; zone of transition from sternite to genital bay densely covered with medially directed trichia of various sizes, some arising from papillar but non-alveolar bases; posterior margin of sternite VIII on either side of genital bay with a more or less distinct peak to posterior. Vaginal floor conspicuous in ventral view as a pair of darkened, anteromedially narrowly fused areas; anterior and lateral margin of floor with narrow sclerotization that is posteriorly connected to the gonocoxapodeme VIII; dorsal (intra-vaginal) surface of floor with loosely spaced microtrichia. Gonocoxapodeme VIII nearly straight, extending from dorsal of anteromedial margin of floor to near posteromedial peak of sternite VIII, hardly reaching farther lateral than coxosternapodeme. Gonapophysis VIII with closely adjacent, indistinctly separable lobes. Dorsomesal lobe anteriorly parallel to inner margin of floor with greatest width near posterior end. Ventrolateral lobe arising anteromedial of posteromedial peak of sternite VIII, apparently consisting of two membranous lobes with microtrichia and fine dissections along its medial margin. Apodeme lobe with conspicuous transverse apodeme dorsal of posterior end of dorsomesal lobe, and with extensive soft membrane to medial and posterior that carries many trichia and fine striations on its margin and at least anteroventral surface. Notum extending through most of length of segment VIII, much longer than seminal capsule, free rami very short or indistinct. Seminal capsule ovoid, spermathecal duct nearly straight, carrying secretory cells, subapically narrowing, the two ducts meeting at their joint opening. Coxosternapodeme with extensive anterolateral part carrying a diagonal dorsal ridge, and with narrow anteromedial and posterior extensions. Labium with diagonal internal apodeme and fine to spinose chaetulae on dorsomedial surface.

Tergite IX shallowly hemispherical, with setae indistinctly separated in two groups, and with a posteromedial brown streak that leads towards a sclerotized external tubercle. Gonocoxite IX with dorsal, lateral and ventral setae. Segment X without setae, ventrally with large triangular postgenital plate, dorsally with even longer mediocaudal projection. Cercus long with anterior end curving to lateral where it is fused to segment X.

Systematics

The new genus is similar to the other genera of the tribe Psudochironomini in having a black comb on the apex of the fore tibia, similar to the combs on mid- and hind tibiae. The males of the genera Manoa , Pseudochironomus and Riethia all lack an anal point, while Aedokritus has a triangular anal point covered with microtrichia at least in basal one half, and Megacentron erebus (Skuse, 1889) has a rather narrow, spatulate anal point apparently without microtrichia except at base. The male of the new genus has a strong, moderately long, nearly parallel-sided anal point with broadly rounded apex, without microtrichia except at base. It also has a has a digitiform, apically split median volsella with strong brush-like setae, projecting medially, while both Aedokritus and Megacentron have median volsellae projecting caudally. The female genitalia are complex, differing quite strongly from the genitalia of Pseudochironomus and Manoa as described by Saether (1977a), particularly in the shape of gonapophysis VIII.