Hydrosmittia, Ferrington Jr & Saether, 2011

Ferrington Jr, Leonard C. & Saether, Ole A., 2011, A revision of the genera Pseudosmittia Edwards, 1932, Allocladius Kieffer, 1913, and Hydrosmittia gen. n. (Diptera: Chironomidae, Orthocladiinae) 2849, Zootaxa 2849 (1), pp. 1-314 : 103-105

Hydrosmittia gen. n.

Type species: Pseudosmittia ruttneri Strenzke et Thienemann, 1942: 352 .

Other included species: H. aagaardi sp. n., H. annulata sp. n, H. brevicornis (Strenzke) comb. n., H. falsicostata sp. n., H. kisotriangulata (Sasa et Kondo) comb. n., H. montana (Strenzke) comb. n., H. oxoniana (Edwards) comb. n., H. setavena (Saether) comb. n., H. soelii sp. n., H. tenuistylata sp. n., H. togadistalis (Sasa, Watanabe et Arakawa) comb. n., H. virgo (Strenzke) comb. n.

Diagnostic characters: The imagines are separable from other Orthocladiinae with bare eyes, wings and squama, by having 2 (or when 3, as in some H. ruttneri , the third much weaker) short, mostly biserial acrostichals on midscutum without additional tubercle, hump or microtrichial tuft; non-extended, non-protruding eyes; palp not reduced; median antepronotal lobe well developed; supraalar absent; anal lobe of wing mostly well developed and projecting, occasionally weak, but not reduced; costa not to slightly extended; VR high, but at most 1.5; R 4+5 ending distal to, above or slightly proximal to end of M 3+4,; Cu 1 distinctly sinuous; postcubitus never forked; male anal point absent or placed forward on tergite IX with weak microtrichia reaching to apex or apex bare, occasionally absent (some specimens of H. ruttneri ); single, plate-like, median virga with additional pair of lateral rows of spines [except in H. togadistalis (Sasa, Watanabe et Arakawa) ]; pars ventralis and superior and median volsellae absent; male gonostylus simple; female genitalia with gonocoxite IX long and low with characteristic sclerotized margin against tergite IX; small dorsomedian lobe; large ventrolateral lobe; and spermathecal duct with loop.

The pupae can be separated from other orthoclads by lacking a thoracic horn and a precorneal tubercle, having tergites II–VII with similar-sized spinules covering most of tergites, frontal setae often on prefrons or absent, reduced or smoothly rounded anal lobe without or with fine hair-like setae; three precorneals and two median antepronotals all fine and hair-like, and usually conjunctives both dorsally and ventrally armed with spinules.

The larvae are separable from all other orthoclads except Camptocladius v. d. Wulp, Allocladius Kieffer and Pseudosmittia Edwards by having broad, bifid S I and S II, reduced antenna and no procerci. They differ from Camptocladius by having premandible with brush, and relatively well developed posterior parapods with claws. They differ from Pseudosmittia by having 7–11 claws on posterior parapods as opposed to 0–5 claws or 8 claws in P. mathildae with inner tooth of mandible hook-shaped, and antennal blade at most twice as long as width of basal antennal segment; from most Allocladius by having a mandible with 3 inner teeth, or when with 4, mentum with 4 pairs of lateral teeth and anterior parapods without longer claws.

Description

Imago

Small to medium sized species, wing length 0.95–2.7 mm. Coloration brown to black.

Eyes without dorsomedian elongation, bare. Male antenna with 13 flagellomeres, occasionally division between terminal flagellomeres incomplete; fully plumed; antennal groove beginning on flagellomeres 3 to 4; sensillae chaeticae on flagellomeres 2, 3 and 13; apex without subapical seta. Antennal ratio of male 0.15–2.02. Female antenna with 5 flagellomeres; 1 pair of broad sensilla chaeticae on each of flagellomeres 1–4; 1 broad pair, 0–1 relatively wide and about 20–30 slender, curved sensillae chaeticae on flagellomere 5, apical seta absent. Antennal ratio of female 0.39–0.73. Temporals uniserial; consisting of 0–9 isolated usually very weak inner verticals, absent only in H. ruttneri and H. brevicornis , more than 5 only in H. annulata , long only in H. oxoniana ; 1–7 outer verticals; and 0–3, usually none, postorbitals normally not separated from outer verticals. Palp 5 segmented, third palpomere with 1–6 lanceolate sensilla chaetica; fourth palpomere without sensilla chaeticae.

Antepronotal lobes well developed medially, with 1–3 weak lateral setae. Acrostichals 2 side by side on midscutum, dorsocentrals usually uniserial, 4–12; prealars 1–6; supraalar absent. Scutellum with 2–10 uniserial setae.

Wing membrane without setae, with moderately coarse punctuation of microtrichia, occasionally tinged with grey or brown. Anal lobe well developed and projecting to weak, but not reduced. VR 1.16–1.53. Costal extension 0– 103 µm long, often with false vein extending from apex of costa or R 4+5 nearly to wing apex; R 2+3 running medially between R 1 and R 4+5; R 4+5 ending distal to, above or slightly proximal to end of M 3+4,; Cu 1 distinctly sinuous; postcubitus never forked; Cu 1 distinctly sinuate; FCu ending far distal to RM; postcubitus extending well beyond FCu, never forked; anal vein shorter than postcubitus. Brachiolum with 1 or occasionally 2–3 setae; R usually without setae in male, occasionally with 1–13 setae, with 4–9 setae in examined females; R 1 nearly always without setae in male, occasionally with 1–3 setae, with 1–8; R 4+5 nearly always without setae in male, occasionally with 1–4 setae, with 5–14 setae in female; costal extension with 0–1, usually 0, non-marginal setae in male, with 1–20 in female; costa between above RM and apex of R 4+ 5 in female with 0–42 non-marginal setae, absent only in H. oxoniana . Squama bare. Sensilla campaniformia about 8–10 on base of brachiolum, 3 below setae and about 10–12 at apex of brachiolum, 1 on base of subcosta, 1 on FR and 1 on base of R 1.

Tibial spurs long and well developed on all legs. Hind tibial comb always well developed, consisting of 9–18 setae, less than 10 only in some specimens of H. soelii . Mostly weak relatively pale, occasionally strong, pseudospurs present at apex of ta 1 to ta 4 on all legs and often medially on ta 1. Sensilla chaetica absent. Pulvilli small, vestigial or absent.

Tergites with irregularly arranged setae, in anterior and median transverse rows with some lateral setae, or only a few setae in an anterior transverse row. Tergite IX of male with 9–29 setae. Anal point base placed anteriorly on tergite, 0–57 µm long; with or without basal setae, with weak microtrichia reaching to apex or apex bare, occasionally absent (some specimens of H. ruttneri ); usually narrowly triangular, sometimes broadly triangular, occasionally rounded or narrowly parallel-sided. Sternapodeme straight or arched, oral projections absent in H. annulata , H. soelii and H. tenuistylata , well developed in the other species. Phallapodeme distinct, with two strongly sclerotized apical teeth in H. togadistalis , teeth indicated also in H. tenuistylata and a corresponding apical projection in H. soelii and H. annulata . Virga consisting of median, single plate and additional lateral rows of 6–30 more or less triangular spinules, absent only in H. togadistalis , often difficult to observe, but very strong in some species; median virga 9–57 µm long. No pars ventralis. Gonocoxite 2–3 times as long as gonostylus. Superior volsella absent, or bulge-like; inferior volsella single or more often with accessory lobe which may be adpressed to gonocoxite or free at apex. Gonostylus variable in shape, broadest at base or at apex, tapering or parallel-sided, with or without well developed crista dorsalis, with or without outer heel; megaseta single, sclerotized, 6–14 µm long.

Tergite IX of female slightly to strongly divided into two setigerous protrusions separated by caudal notch, with altogether 12–23 setae; with characteristic sclerotized margin or apodeme against low but long and adpressed gonocoxites to each side. Gonocoxite with 2–5 strong setae and 2–6 weaker setae. Gonapophysis VIII divided into small dorsomesal lobe widest in the middle, and large ventrolateral lobe. Apodeme lobe often distinct, often with parallel margins. Postgenital plate weak. Cerci of moderate size, shorter than length of notum, occasionally only half as long. Seminal capsules usually ovoid, occasionally circular, with large neck, often with microtrichia, without striations; dark sclerotized in apical 4/5; spermathecal ducts with loop, apparently without bulbs or widening before openings.

Pupa

Small to medium-sized pupae, length 2.0– 3.8 mm. Exuviae infuscate on thorax, weakly infuscate on abdomen or nearly transparent.

Frontal setae present except in H. ruttneri , H. falsicostata and H. virgo , on frontal apotome, hair-like and 10– 80 µm long in other species. Frontal warts absent to distinct; frontal apotome smooth, occasionally wrinkled or with spinules or tubercles. Ocular field at least with 1–2 postorbitals.

Thorax with 2 median and 1–2 lateral antepronotals. Thoracic horn and precorneal tubercle absent. Three fine hair-like precorneals; 4 dorsocentrals, 3 posterior ones usually close together. All cephalothoracic setae fine and hairlike and not possible to measure accurately. Thorax smooth or occasionally with a few spinules. Wing sheath smooth, without pearls and nose. Leg sheaths recurved beneath and not extending beyond apex of wing sheaths.

Tergite I bare, with weak to strong anterolateral shagreen, occasionally with caudolateral shagreen, or with both anterolateral and caudolateral shagreen; tergites II–VII with shagreen consisting of similar-sized spinules covering most of tergites; tergite VIII with or without preapical area devoid of spinules; tergite IX usually with shagreen covering most of segment, occasionally with anterior and/or median shagreen only, occasionally bare. Tergal conjunctives II/III or III/IV to VI/VII or VII/VIII with rows of hooked spinule. Sternites I–IV bare or usually variable shagreened with fine spinules, sternite V usually with fine anterior and posterior shagreen, sternites VI–VIIII with more extensive and coarse shagreen, sternite IX bare or with anterolateral and anteromedian shagreen. Sternal conjunctives with spinules of equal size to those on tergal conjunctives on III/IV or IV/V or V/VI to VII/VIII (in most females) or to VIII/IX in most males. Apophyses weakly indicated. Pedes spurii A and B absent. Tergite I with 3 D setae, VIII with 2 D setae. Segment I with 3, II–VIII with 4 hair-like L setae. Apparently only 1 pair of dorsal O setae.

Anal lobe reduced, rounded without setae or with 2–3 anal macrosetae and 1 basilateral hair-like seta, with or without additional median seta. Male genital sac extending well beyond anal lobe, female genital sac reaching apex of anal lobe or extending slightly beyond; genital sac bare or with basal, ventral spinules, with or without additional apicolateral spinules or nearly covered by spinules; occasionally with apical papilla.

Larva

Medium-sized larvae, 1.8–6.2 mm long.

Antenna about 1/4 length of mandible; 4 segmented; basal segment at least as wide as long, occasionally nearly twice as wide as long; with apical ring organ (? always) and 2 oval sensilla basiconica at margin; with blade at least as long as width of basal antennal segment, extending beyond flagellum; accessory blade as long as second or second and third segment combined. Second segment often sclerotized at base only, with large unsclerotized apical portion; subapical style characteristically pyriform; Lauterborn organ often indistinct, but large in comparison with antennal segment; segments 3 and 4 usually subequal in length, both shorter than second segment.

S I and S II both broad and bifid with basal collar particularly on S II, chaetae transversales present or absent or absent laterally to S II, chaeta media sometimes conspicuous, 0–2 spinulae. Pecten epipharyngis and median 2–4 chaetulae laterales consisting of simple scales, lateral 2–4 chaetulae laterales pale and strongly divided; chaetulae basales weak, pointed, single or split to base. Premandible with 2 apical teeth and 1–2 more or less tooth-like inner projections, with distinct brush. Mandible with 3–4 inner teeth, with or without 2 additional dorsal teeth; seta subdentalis usually present; seta interna absent or present, well developed and 6-branched in Hydrosmittia sp. Northwest Territories, weak with 4–5 branches in H. ruttneri , absent or not observed in all other species. Mentum with single median tooth with or without median projection, 4–5 pairs of lateral teeth, and large ventromental plates not extending beyond outer teeth on flattened mentum; beard absent. Maxilla with appendix seta and antaxial seta well developed; lacinial chaeta short, anterior lacinial chaeta not differentiated; pecten galearis and lamellae of galea absent; chaetulae of palpiger few, simple and scale-like; and maxillary palp well developed with two distinct levels. Prementohypopharyngeal complex with median lamellae highly divided and serrated appearing as consisting of several toothed lamellae; paramedian lamellae also highly toothed, but with common base; pecten hypopharyngis consisting of scales with apical teeth for half their length.

Anterior parapods fused, with narrow basal spinules, each parapod with about 20–60 larger serrated claws, occasionally ( Hydrosmittia sp. “ Northwest Territories ”) without longer claws. Posterior parapods vestigial to relatively long and slender (up to 200 µm long) with 7–12 smooth or serrated claws. Procercus absent, 1 anal seta or occasionally 2 (some H. ruttneri ) or 3 ( H. falsicostata ) anal setae. Two pair of anal tubules present, ventral pair usually larger than dorsal pair, occasionally with 1–2 constrictions, largest tubules usually subequal in length to length of posterior parapods, or when parapods vestigial, much longer than parapods.

Body setae very thin, hair-like and simple, often not discernible.