Paucispinigera approximata Freeman
Cranston, Peter S., 2020, Life histories of Paucispinigera Freeman, Paraborniella Freeman and Paratendipes Kieffer (Diptera: Chironomidae) with phylogenetic considerations, Zootaxa 4853 (4), pp. 527-547: 529-534
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|Paucispinigera approximata Freeman|
Material examined: 2♂, Pe / ♂, 8 Pe , NEW ZEALAND: South Island , Nelson Lakes N.P., Speargrass Stream, 41°47’01”S 172°46’28”E, 1.ii.2000 (Cranston); GoogleMaps 7L, same except 41°48’24”S 172°50’46”E, 13.vi.2007 (‘QUT team’); GoogleMaps L, same except 11 –13.i.2010 (Cranston) MV NZ 10–2. GoogleMaps
Description. Adult Male (n=2). Body length 2.5–3.0 mm, wing length 2.2 [2–2.6] mm. Wing hyaline, plain. Slide mounted colour: thorax yellow-brown with darker postnotum, legs plain [“green with reddish thoracic markings ... head and antennal pedicel yellow, palpi darker .... thorax yellowish-green with reddish strips, postnotum and sternopleuron ... legs pale yellow ..... abdomen plain green”]
Antenna. With 13 flagellomeres; Fl 1-12 500–510, Fl 13, 560–570; Antennal ratio 1.1–1.2 [1.3].
Head. Eye bare, with dorsomedial parallel-sided extension 5 ommatidia long, separated medially by width of 8 ommatidia. Temporals 10–12 uniserial; clypeals 7–8. Frontal tubercles absent. Palp 5-segmented, segment 2 globular, segments 3 and 4 approximately equal in length, 5th long (250 μm); segment 3 apparently lacks sensilla.
Thorax. Antepronotal lobes tapered dorsally, medially divided at notch, without lateral antepronotal setae. Scutum not overreaching antepronotum, smoothly curved in profile. Without any humeral pit. Ac (c. 12) partially biserial, starting from front, ending just anterior to scutellum; 6–7 uniserial Dc each arising from pale spot, absent from humeral area; 3 Pa; 6–8 uniserial Scts.
Wing ( Fig. 1A, B View FIGURE 1 ). Membrane without setae or microtrichia. Anal lobe weakly developed. Costa ends at apex of long R 4+5 terminating at wing tip, close to apex of M 1+2; R 2+3 tracking close to R 1. FCu distal to RM with VR 1.3–1.4. Brachiolum with 2 setae. R, R 1, R 4+5 and distal half of M 1+2 setose. Squama bare [fringed].
Leg. Apex of fore Ti with rounded scale, without spur ( Fig. 1C View FIGURE 1 ). Mid and hind Ti apically with two nearly contiguous combs occupying about 60% circumference, one comb with curved spur ( Fig. 1D View FIGURE 1 ), the other without spur. Only teneral LR 1 available, c. 1.2 [1.3]. Pulvilli absent [only visible in slide preparations and not divided]; empodium well formed.
Abdomen. Tergites I–VII with few irregularly scattered setae.
Hypopygium ( Fig. 1E, F View FIGURE 1 ). Anal tergite without evident bands, mictrotrichiose to base of anal point, with median anal tergite setae represented by few small setal bases; few short basal-lateral setae on submargin of tergite IX. Anal point near continuous taper from anal tergite margin, short, bare apically, with rounded apex. Superior volsella ( Fig. 1E View FIGURE 1 ) broadly digitiform (‘fat finger’), abruptly narrowed distally to curved hook, with coarse microtrichia basally, with 2-3 stronger setae dorsally, 2 medially-directed on inner surface, bare apically. Median volsella with distinct stem, distally with 3-5 long simple narrow taeniae, directed medially ( Fig. 1F View FIGURE 1 ). Inferior volsella fused to gonocoxite in basal 1/3, becoming subglobular, extending beyond gonocoxite apex, microtrichiose apico-ventrally, apically with medial to dorsomedial directed, simple setae, without any differentiated apical seta. Gonostylus sickle-shaped or ‘allantoid’, inward curving with rounded apex bearing a small ‘megaseta’ (i.e. seemingly with ‘socket-base’) or simple point. Transverse sternapodeme and phallapodeme (not illustrated) very pale, indistinct (hypopygia examined are teneral).
Adult female (described briefly by Freeman, 1959) (n=0). Distinguished by bare squama, wing veins R 4+5 and M 3+4 ending close at wing apex; all R veins and both M veins setose.
Pupa (n=8). Medium-sized, c. 4.5–5.0 mm long. Thorax and cephalic area pale golden brown, abdomen pale hyaline with indication of darker golden apophyses, comb and anal lobe.
Cephalothorax. Frontal apotome weakly wrinkled, without cephalic tubercles or frontal warts; frontal setae (90 μm) located on short, sometimes pointed tubercle (5 μm) ( Fig. 2A View FIGURE 2 ). Detail of thoracic horn difficult to interpret but with plump, spinose, basal stem (c. 100 μm long), divided into few, possibly only 2, maximally 4, hyaline branches; basal ring small, oval and with modest tracheal ‘bundle’. Median suture rugulose with small scales ( Fig. 2B View FIGURE 2 ). Prealar tubercle absent. Antepronotum with 1 median, 0 lateral setae; 2 precorneals; dorsocentrals (Dc) each c. 50 μm long with Dc1 and Dc 2, approximated and well separated (250 μm) from also closely approximated Dc 3 and Dc 4.
Abdomen ( Fig. 2C View FIGURE 2 ). Tergite I bare, II–VI each with extensive subquadrate spinule patch without stronger anterior or posterior bands; T VII–VIII and anal segment bare. Tergite II hook row continuous, comprising 20–25 hooks, 25–30% width of segment II. Narrow transverse spinule bands on conjunctives III and IV. Segment V with fine pale spinules in patch on posterolateral of pleura ( Fig. 2D View FIGURE 2 ). Sternites III–VI with fine spinules (max. length 6 μm), extensive on III, with at least anteromedian patch on IV–VI; remainder bare. Vortex on IV. Pedes spurii B strong, on segment II only. Posterolateral corner of segment VIII (‘comb’) with golden–brown teeth, posteriormost tooth dominant, with 2–4 shorter, curved, pointed teeth ( Fig 2E View FIGURE 2 ). Apophyses weak. Segment I with 2D, 3V and without L setae; II with 3D, 3V and 3 L; III with 4D, 3V and 3L; IV–VII with 5D, 3–5 V and 4 taeniate LS, VIII with 4 taeniate LS. O setae very fine, present definitively on TII–V, uncertain otherwise, but at least on SIII. Anal lobe elongate semicircular with uneven uni-biserial fringe of 22–27 taeniae, with fine dorsal seta. Genital sac of male extends beyond anal lobes, of female unknown or male-like.
Larva (4th instar) (n=5). Body ( Fig. 3A View FIGURE 3 ) pink-red in life 4–4.5 mm long, ventral head length 350–380 μm. Head capsule yellow with golden-brown dorsomental, apical mandibular and premandibular teeth. Genae and submentum variably darkened; occipital margin broad, dark.
Dorsal surface of head ( Fig. 2F View FIGURE 2 , 3B View FIGURE 3 ) with frontoclypeus narrowing anterior prior to subterminal flare to lateral points, without frontal pit. Cephalic S3 (clypeal) setae close to anterior margin, S2 seta on narrow granulose area, S1 on delimited labrum—all 3 setae (S1–S3) forming a tight cluster.
Antenna ( Figs 2G View FIGURE 2 , 3C View FIGURE 3 ) 6-segmented, with segments 2 and 3 subequal, each longer than short 4th, 5th longer than 4th, 6th shortest; Lauterborn organs well developed, sessile, alternate on apices of 2nd and 3rd segments. Segment 1 with ring organ at basal third, seta absent. Blade subequal or extending slightly beyond antennal apex.
Labrum ( Figs 2H View FIGURE 2 , 3D, E View FIGURE 3 ). SI arise near contiguous on fused base, broadly plumose with about 20–25 apical branches; SII arise from nearly contiguous short tubercles, apically serrate on both margins; SIII simple, short; SIV moderately developed. With 7–8 plumose chaetae. Seta praemandibularis simple. Labral lamellae a broad, single plate with fine teeth. Pecten epipharyngis comprising three separate lobes each with 2–4 rounded teeth. With 7–8 apically plumose chaetulae laterales and 2 apically branched chaetulae basales. Premandible with 4 teeth, distal pair more pointed than shorter, rounded, inner pair, with strong brush.
Mandible ( Figs 2I View FIGURE 2 , 3F View FIGURE 3 ) with short pale dorsal tooth, larger triangular apical tooth and 2 modest inner teeth; darkened distal mola not tooth-like. Pecten mandibularis with 8–10 branches, strong, extending to margin of mandible. Seta subdentalis very elongate, arising from ventral surface of mola, significantly retracted on mola, somewhat dilate medially then narrowing to rounded apex, level with apical mandibular tooth. Mola and inner margin smooth. Seta interna densely plumose, located more basal than usual.
Mentum ( Figs 2J View FIGURE 2 , 3G, H View FIGURE 3 ) with fully delimited ventromental component of 8, uneven-sized, slightly paler median teeth; dorsomentum on each side with 4 darker teeth each diminishing slightly in size laterad. Ventromental plate fan-shaped with curved anterior margin, with notch at level of dorsomental teeth, striae numerous, almost straight, fine. Setae submenti simple.
Body ( Figs 3A, I View FIGURE 3 ). Without lateral or ventral tubules. Anterior parapod claws dense, fine, simple, pale; posterior parapods claws pale, simple. Procercus pale, small, as high as wide, bearing 7–8 anal setae.
Discussion. The adults of Paucispinigera were described by Freeman (1959) from New Zealand from a small fauna lacking many genera with which to make comparisons. The Australian Chironomidae were under revision and to be described shortly thereafter ( Freeman 1961), and must have been known to him. In this context, Saether’s (1977) provisional key to female adults, using non-genitalic features for both sexes derived from Freeman (1959, 1961) to distinguish Paucispinigera and Paraborniella remains valid: squama bare, pulvilli near absent, non-extended scutum, anterior tibia with rounded scale and without spine. The distinctive wing venation of Paucispinigera , with R 4+5 and costa extending to wing apex near an upturned apex of M 1+2, and setosity of M veins continues to allow differentiation, as does the unusual ‘megaseta’ on the apex of the male gonostylus. These wing characters could be considered as autapomophic (providing no ranking information) and no additional evidence is provided by the female genitalia. As discussed below, Paucispinigera and Paraborniella key in Cranston et al. (1989) with Apedilum and Paralauterborniella , but neither are convincing given substantial differences in the male genitalia.
Differentiation in pupae at the generic level, in contrast to the efficacy at species level, is plagued by lack of autapomorphies within excessive variation. In Pinder & Reiss (1986) the pupa of Paucispinigera can be keyed to Paratendipes , including with the large pedes spurii B, but differing from most in lacking cephalic tubules and warts, and in the distribution of taeniate L setae.
In the regional key of Cranston (2019b) the larva of Paucispinigera is separated from similar genera with a 6 segmented antenna and displaced Lauterborn organs, including Microtendipes , Paratendipes and Paraskusella ( Cranston 2018) by differences in the pigmentation and teeth number and relative height of the median (ventro-) mentum structure. The paired low (small) teeth in a mid-ventromentum of 8 delimited teeth appear diagnostic.
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