Sigmoitendipes, Andersen & Mendes & Pinho, 2017

Andersen, Trond, Mendes, Humberto Fonseca & Pinho, Luiz Carlos, 2017, TWO NEW NEOTROPICAL CHIRONOMINAE GENERA (DIPTERA: CHIRONOMIDAE) Abstract, CHIRONOMUS Journal of Chironomidae Research 30 (30), pp. 26-54 : 39-41

Sigmoitendipes new genus

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Type species: Sigmoitendipes susanae n. sp.

Other included species: Sigmoitendipes fittkaui n. sp., S. oliveirai n. sp., S. reissi n. sp. and S. spiesi n. sp.

Etymology: The specific epithet refers to the shape of the superior volsella resembling the lower-case Greek letter sigma. The suffix - tendipes is a common ending among Chironominae genera. For the purposes of nomenclature, the gender of the genus name is masculine.

Diagnostic characters

The males can be separated from all other Chironomini by the combination of an antenna with 13 segments, antennal ratio about 2.0; squama with 5–11 setae; wings lacking markings; fore tibia with well-developed, bearded scale, comb of mid tibia with one spur, comb of hind tibia with two spurs; anal tergite bands weak, adjacent to anterior tergite margin, in some species with short median longitudinal extension; setae on tergite IX restricted to posterior margin and/or base of anal point; anal point strong, spatulate; superior volsella complex, composed of a median or ventral, rounded or subrectangular part densely covered with microtrichia and carrying a few setae in some species, and of a dorsal to apical part with several strong setae and in some species with sparse microtrichia, dorsal part with apex more or less hooked; inferior volsella near mid-length with bluntly triangular dorsal lobe.

The pupa shares with those of some other Chironomini the combination of long, robust frontal setae; well-developed, conical cephalic tubercles; strongly plumose thoracic horns; anterior, transverse bands of shagreen on tergites II–VI; robust, longitudinal anal combs; and no dorsal setae on the anal lobes. It can be separated by having only one median antepronotal seta, and 5 LS setae on segment VIII.

The larva has a six-segmented antenna with a single well-developed Lauterborn organ on the second segment; the mandible has one dorsal, one apical and four inner teeth, with the seta subdentalis long, slender and straight; the mentum with 8 pairs of equally sclerotized teeth, the first lateral teeth larger than the median pair, the second lateral teeth smaller than both their immediate neighbours, and the further lateral teeth decreasing progressively to a minute seventh tooth; and the ventromental plates slightly wider than the mentum, and separated by the width of 4–5 mental teeth.

Generic description

Male. Medium sized species, wing length 1.9–2.2 mm.

Coloration. Body brown, wing translucent without dark markings.

Antenna. With 13 flagellomeres. AR 1.93–2.27.

Head. Eyes bare, with well-developed dorsomedial extension, with 6–7 ommatidia in first transverse row. Frontal tubercle indicated as paler area to small knob. Temporal setae 10–30, partly biserial, composed of 2–4 inner verticals, 5–15 outer verticals and 3–13 postorbitals. Clypeus with 10– 25 strong setae. Palp with 5 segments, not shortened; third palpomere with 3–8 sensilla subapically, longest 22–27 µm long.

Thorax. Antepronotal lobes narrowly separated medially, each lobe narrowing dorsally. Scutum not overreaching antepronotum, tubercle absent or weak. Acrostichals 5–10, erect, starting some distance from antepronotum. Dorsocentrals 5–11, uniserial; prealars 2–5; supraalar absent. Scutellum with 7–13 setae, uniserial to partly biserial.

Wing. VR 1.07–1.13. Wing membrane bare, with fine punctation. Anal lobe well developed. Costa not extended, ending opposite to M 1+2; R 2+3 ending in proximal 1/3 between apices of R 1 and R 4+5; FCu slightly distal to RM. Brachiolum, R, R 1 and R 4+5 with setae, remaining veins bare. Squama with 5–11 setae.

Legs. Apex of fore tibia with rounded, unspurred scale, with long beard. Mid- and hind tibiae with fused combs, mid tibia with single spur, hind tibia with two spurs. With one pair of pseudospurs on ta 1 –ta 3 on mid- and hind legs; sensilla chaetica apparently absent. Pulvilli simple, lobe-shaped, shorter than claw. LR 1 1.51–1.71.

Abdomen. Tergites and sternites moderately to densely setose with irregular setae. Segment VIII tapering slightly anteriorly.

Hypopygium. Anal tergite bands weak, following anterior margin of tergite. Tergite IX with posterior margin subtriangular, with few marginal setae to each side of anal point only. Anal point long, spatulate, with microtrichia at base only. Laterosternite IX with few setae. Transverse sternapodeme narrow, straight or sinuous, without oral projection. Phallapodeme normal. Superior volsella without setose base, complex; with median or ventral, rounded or subrectangular lobe densely covered with microtrichia, with or without a few apical setae; with dorsal to apical lobe, without or with sparse microtrichia, with several strong setae, apically hooked with apex projecting laterad. Median volsella absent. Inferior volsella long, with narrow base; medially with bluntly triangular, dorsal lobe; apical one-half widened, subrectangular to bluntly subtriangular, with several strong, orally directed setae, distally with one or two longer setae projecting caudally. Gonostylus long, rather stout, widest in apical one-half, subapically with row of short, strong setae along inner margin. HR 0.73–0.95.

Female. Unknown.

Pupa and larva. See description under S. susanae .

Remarks

Larvae of Sigmoitendipes n. gen. may represent the morphotype “ Endotribelos sp. 2 ” (Trivinho-Strixino 2011), with which it appears to share the six-segmented antenna with well-developed Lauterborn organs on the second segment, the mentum with 16 dark teeth of alternating sizes, and the wide ventromental plates. However, the information available on larvae in Sigmoitendipes n. gen. are insufficient for reliable identification with that morphotype. Moreover, the pupal anal comb with about 30 minute teeth that is visible in a pre-pupa of “ Endotribelos sp. 2 ” (S. Trivinho-Strixino, pers. comm.) appears to suggest distinct genera.

Key to males in Sigmoitendipes n. gen.

1. Dorsal lobe of superior volsella subtriangular, broad, with at most the very tip slightly curved. Mato Grosso State. …………….. S. oliveirai n. sp.

– Dorsal lobe of superior volsella narrow, strongly curved. ………………..........………………….. 2

2. Superior volsella with median, rounded lobe with microtrichia, not reaching apex of volsella. .... ............................................................................. 3

– Superior volsella with ventral, subrectangular lobe with microtrichia, reaching apex of volsella. ............................................................................. 4

3. Apical, hooked part of superior volsella with sparse microtrichia and about 10 setae; hook moderately strong. São Paulo, Mato Grosso, Amazonas and Pará States..…...................... S. susanae n. sp.

– Apical, hooked part of superior volsella without microtrichia, with 4 setae; hook very strong. São Paulo State. ...................................... S. reissi n. sp.

4. Ventral, subrectangular lobe of superior volsella narrow, without seta. Mato Grosso and Pará States. ....................................................... S. fittkaui n. sp.

– Ventral, subrectangular lobe of superior volsella comparatively wide, with 2 apical setae. Mato Grosso State. ................................... S. spiesi n. sp.