Micropsectra pallidula, (MEIGEN)

Stur, Elisabeth & Ekrem, Torbjørn, 2006, A revision of West Palaearctic species of the Micropsectra atrofasciata species group (Diptera: Chironomidae), Zoological Journal of the Linnean Society 146 (4), pp. 165-225 : 201-204

MICROPSECTRA PALLIDULA (MEIGEN)

Chironomus pallidulus Meigen, 1830: 255 . Lectotype £ & 1 paralectotype £ by present designation (MNHN) [both examined]. Type locality probably Germany, specimens possibly collected by von Winthem ( Meigen, 1830).

Micropsectra viridiscutellata Goetghebuer, 1931: 111 . Lectotype £ by present designation (NMW) Austria, Nieder-Fladnitz , 20.iv.1916, Zerny; 2 paralectotypes: 1£ as lectotype, 1£ as lectotype except deposited in RBINS [all examined]. syn. nov.

Micropsectra franzi Goetghebuer, 1949: 7 . 2££ syntypes on same slide (RBINS) Austria, Admont, 1948, H. Franz [examined]. syn. nov.

Micropsectra candida Chaudhuri & Datta, 1991: 29 . Holotype £ (UBI type no. 191), Darjeeling, 27°3′N 88°18′E, 2424 m a.s.l., 11.iv.1984, T. K. Datta [examined]. syn. nov.

Micropsectra bidentata Goetghebuer, 1921 ( Brundin, 1949; Lindeberg, 1970; Pinder, 1978; Goetghebuer, 1937 −54; Langton, 1991; Klink & Moller Pillot, 2003; Langton & Visser, 2003; Ekrem & Willassen, 2004) nec Goetghebuer (1921). Misidentifications.

Additional material examined

2££ ( RBINS), Belgium, Bullange 21.ix.1923, G. Severin. Germany ( ZSM): 1£, 1 P(£) & 3 Pex, Bavaria, Memmingen, Benninger Moos , 23.vi.2002 & 17.viii.2002, S. Wiedenbrug; 5 Pex Bavaria, Fürstenfeldbruck , Eichenau , Starzelbach , Höhe Kirche , 4.vii.1998 & 10.v.1998 , leg. F. Reiss; 2 Pex Bavaria, Fürstenfeldbruck, Puchheim , Baggersee , 10.iv.1991, F. Reiss; 1£, Schleswig-Holstein, Redensburg-Eckernförde, Fuhlenau, 9.x.1982, K. Mikowski; 1 P£, 1P(£), 1£ & 2 Pex Hessen, Fulda, 19.v.1953, 23.vii.1952 & (692), E. J. Fittkau; 6££ Nordrhein-Westfalen, Sauerland, Aabach 12.vi.1953 & 24.v.1954, H. Dittmar . Norway ( ZMBN) : 1£, Vest Agder, Kristiansand, Kjosbekken at Storevann , 2.vii.2001, T. Ekrem; 1£, Vest Agder, Vennesla, Skjerkedalsbekken at Åmdal, 6.vii.2001, T. Ekrem; 1 Pex, Kristiansand, Grimsvann / Skjebbekjønn, 2. vii.2001, T. Ekrem; 1£, Hordaland, Osterøy, Låstad, 29.x.1989, A. Fjeldså; 6££ ( VM) , Nord Trøndelag, Høylandet, Skiftesåa , 18.vi.1986, 13.viii.1986, 20.viii.1986, 27.viii.1986, 25.vi.1988 & 24.vii.1988, K. Aagaard & O. Hanssen; 1£ ( ZSM) , Lofoten, Flakstadøy , E Eggum, 12.vi.1990, H. Mendl . Luxemburg ( MGDL) : 1 P(£), Ösling, Groussenboesch, N Bastendorf, 2.viii.1998, R. Gerecke & I. Schrankel; 1 P(£), Ösling, NW Hoscheid, Schlennerbach at Chapelle St. Michael, 22.iv.1999, R. Gerecke & I. Schrankel; 17££ (2 in ZMBN) Ösling, W. Clervaux, helocrene spring no. LUXqu23, emergence trap (E3), 6.iv.1999, 20.iv.1999 & 13.vii.1999, I. Schrankel; 20££, Ösling, E Holzthum, Bleesquelle, helocrene spring no. LUXqu20, emergence trap (E2), 6.iv.1999, 20.iv.1999, 4.v.1999 & 18.v.1999, I. Schrankel; 4££, Gutland, SW Merscheid, rheohelocrene spring no. LUXqu11, emergence trap (E4), 6.iv.1999 & 20.iv.1999, I. Schrankel. 1 P(£) ( ZSM) , Italy, Abruzzia , 20.iv.1978, E. J. Fittkau & B. Rossaro; 2££ ( ZSM) , Morocco, 15 km W of Ljoukak , 1.iii.1966, F. Ringe; 1 P(£), 2 L ( ZMBN) , Scotland, Loch nagar, 14.ix.1991, Ø. A. Schnell; 2££ ( WG) Poland, Kashubia, Czysta Woda , netting on stream, 17.ix.1998, W. Gilka; 10 L, 1 L(P), 4 Pex, 2 P(££), 2 P(££) ( AK) The Netherlands, Gelderland, Eerbeek, Eerbekse Beek , mp. 5, 24.v.1981, A. Klink; 1 L, 1 P(£) as previous in VM; 1 P(£) ( PHL) , Scotland, Perth & Kinross, Dall Burn , 11.vi.1985, P. H. Langton . France ( PHL): 1 P(£) & 1 P(£), Lot, Vinzelle , 5.xii.1995, J. Moubayed; 1 P(£) , Corsica, Restonica , 7.vii.1995; 1 P(£) , Corsica, Asco River , 7.vii.1995, H. Laville. 1 P£ ( PHL) Wales, Clwyd, Tynant , rivulet, 28.v.1978 (H4 Pe 140), P. H. Langton; 1 P (£) ( PHL) , England, Cumbria, Newby, Parkcliffe Caravan Site , 29.vii.1974; 1 P(£) ( PHL) , England, Cumbria, Lake dt, limnocrene nr mountain top, 19.viii.1985, P. H. Langton; 1 P£ ( PHL) , Scotland, Perth and Kinross, Loch Laidon , Sphagnum filled ditch, 24.v.1981, P. H. Langton; 1 P(£) Scotland, Highland Region, Dunbeath, Allt an Learnaich , 31.ix.1989, M. Spirit .

Diagnostic characters

Micropsectra pallidula can be separated from other species in the atrofasciata group by the following combination of characters: Adult male with AR c. 1.1; frontal tubercles minute to very small; pulvilli present, sometimes reaching half length of claws; anal point well developed, comparatively wide at rounded apex, small knob between crests; superior volsella with large field of microtrichia on stem, setiger roundish with straight posteromedian margin, several long microtrichia ventrally on setiger anterior to base of digitus, few wrinkles ventroapically on setiger; digitus long, apically pointed, reaching past posteromedian margin of superior volsella; median volsella long, thin, parallel sided, reaching well beyond superior volsella, apically pointed. Pupa c. 4.3 mm long, with moderately developed, cone-shaped cephalic tubercles; thoracic horn short with comparatively long chaetae on distal 2/3; prealar tubercle low mound, rounded; dorsal granulation along mid suture on thorax; large unpigmented dorsal area on posterior half of thorax; strong spines (40–50 µm long) in patches on tergite III; tergite IV and V with spinules and points only; shagreen in patches on tergite VI; patches on tergite VI of somewhat smaller size than patches on tergites IV–V; large field of microtrichia present between spine patches on tergite III; dorsolateral comb of segment VIII narrow with 4–5 separated, marginal teeth of which 2–4 are larger than the remaining. Larva with comparatively large, straight, usually digitiform spur on antennal pedestal; antennal segment 1 c. 250– 290 µm long; comparatively high AR (c. 2.5) and LOR (6.0–6.9); labral seta SII and some chaetae pectinate; clypeal seta S3 branched with one long branch; MVR about 0.88.

Description

Adult male. Measurements and ratios in Table 1.

Coloration. Body pale greenish with brown eyes, somewhat darker scutal stripes and postnotum.

Head. Antenna with 13 flagellomeres. Frontal tubercles present, small (5–9, 6 µm); temporal setae in one row; palpomere three with c. 5 sensilla clavata apically.

Wing. Subcosta bare, media bare or with 1 basal seta, brachiolum with 2 setae, squama bare; cell m with 70–100 setae.

Legs. Pulvilli present, usually small, sometimes reaching half length of claws. Fore tibia with small scale, 28–40, 35 µm long spur; middle and hind tibial combs, respectively, 18–22, 20 and 25–28, 27 µm long; middle tarsomere Ta 1 with 2–4, 3 sensilla chaetica.

Hypopygium ( Fig. 14A–C ). Anal tergite with tergite bands separate, posteriorly directed, not reaching crests of anal point; 3–6, 5 median tergite setae placed on an elevated hump anterior to anal point base; 9–14, 11 ventral apical setae. Anal point well developed with broad apex; high, slightly curved anal crests; small knob between crests present; large microtrichia free area around base. Setiger of superior volsella roundish with straight posteromedian margin, 5–7, 6 dorsal and 2–3 median setae on setiger, 1 strong seta on stem; large field of dorsal microtrichia on stem and several long microtrichae ventrally on setiger, anterior to base of digitus. Digitus long, apically pointed, reaching beyond median margin of superior volsella. Median volsella comparatively long, thin, parallel sided, pointed at apex, with setiform and medially directed spoon-shaped lamellae, c. 25 spoon-shaped lamellae on distal 1/4–1/3; stem reaching well beyond superior volsella. Inferior volsella with small dorsoapical, medially directed swelling, otherwise quite straight, bearing numerous distal setae. Inner margin of gonocoxite with 3–4 strong setae.

Pupa. Coloration: pupal exuviae brownish with dark brown apodemes; cephalothorax, TVIII and anal lobe darker; large pigment-free area dorsally in posterior half of thorax. Measurements in Table 2.

Cephalothorax ( Fig. 14D, E ). Cephalic tubercle present, medium sized, cone-shaped; pedicel sheath tubercle weakly developed. Thoracic horn fairly short with numerous comparatively long chaetae on distal 2/3; 2 anteriormost precorneals situated closer to each other than to the third, median precorneal shorter than other two; 1 median antepronotal, 2 lateral antepronotals (1 sensillum basiconicum); 2 pairs of dorsocentrals, anterior pair considerably shorter and weaker than posterior pair, Dc 1 longer than Dc 2. Dc 3 and Dc 4 equally long. Some granulation present along median suture line and in small dorsal field on mid thorax. Prealar tubercle small, roundish; nose of wing sheath weakly developed.

Abdomen ( Fig. 14F, G ). TII extensively covered by shagreen except for one posteromedian oval patch, somewhat less shagreen anteriorly on tergite; pedes spurii B on TII obvious; hook row about half as long as segment width. Spines of TIII in large, laterally curved patches in posterior half of tergite, shagreen extensively distributed lateral and anterior to spine patches, numerous points between patches. Patches of TIV consisting of spinules in anterior, oval patches and in longitudinal, lateral, straight extensions; some shagreen present laterally to longitudinal patches. Patches of TV similar to those of TIV in shape and size, consisting of points and spinules. Patches of TVI consisting only of shagreen, similar to patches on TIV and TV in shape. TVII and TVIII bare or with longitudinal oval shagreen patches ( TVII). Segment I with 3 D and 1 V setae; segment II with 3 D, 4 V, 2 L, 1 semitaeniate seta; segment III with 5 D, 4 V, 2 L, 1 lateral taenia; segment IV with 5 D, 4 V, 0–2 L, 1–3 lateral taeniae; segment V with 5 D, 4 V, 3 lateral taeniae; segment VI with 5 D, 4 V, 4 lateral taeniae; segment VII with 5 D, 4 V, 4 lateral taeniae; segment VIII with 1 dorsal taenia, 1 ventral taenia, 5 lateral taeniae; anal tergite with 1 dorsal taenia. Two pairs of small sensorial setae medially on TII–VII; 1 pair of O-setae present anteriorly on sternites II–VII. Anal lobe with evenly convex lateral margins, fringe with about 550–650 µm long taeniae in 1 row. Posterolateral comb of segment VIII ( Fig. 14H ) narrow, with 2–4 marginal teeth longer than rest.

Larva. Head capsule well sclerotized and dark brown. Live individuals were not available for examination. Total length 6.0–6.5 mm. Measurements and ratios in Table 3.

Head ( Fig. 14I–K ). AR about 2.5; antennal pedestal with comparatively long (c. 42 µm), usually digitiform spur; antenna with segments 1–2 well sclerotized, segments 3–5 pigmented, antennal seta placed at about 2/3 length of antennal segment 1; Lauterborn organs small, on very long pedestals; SII and inner chaetae pectinate or plumose; outer chaetae and chaetulae simple, S3 with 3–4 branches; mentum with well developed lateral notches on somewhat pale median tooth; ventromental plates evenly curved with obvious striation along whole length; premandible with 2 robust teeth, inner tooth broader, well developed brush; mandible with pecten mandibularis slightly convex; postoccipital plate comparatively large, subtriangular.

Body. Anterior prolegs with long, simple spines; hind prolegs with numerous (c. 50) simple hooks in two rows; supraanal seta sturdy, visible under 40× magnification, 110–125, 118 µm long.

Remarks

The Meigen collection in Paris contains two specimens under Chironomus pallidulus , both with hand-written ‘Meigen’ labels. Additional, presumably original, labels are on specimen 1: ‘pallidulus £’, ‘189–40’, and on specimen 2: ‘189–40’. Since Meigen’s (1830) very brief description is based on more than one individual, we believe them to be syntypes although only one specimen (no. 58/1) bears a presumably original name label. Both specimens are now mounted in Euparal, but only specimen no. 58/1 has its hypopygium preserved. This specimen is chosen as lectotype to stabilize nomenclature. The other specimen (no. 58/2) has lost its abdomen, but due to the unusually short maxillary palps on the head ( Fig. 15 ) it is clear that this specimen is not conspecific with specimen no. 58/1. Since at least one comb on the mid tibia carries an obvious spur, this specimen may not even belong to Micropsectra .

The specimen of Micropsectra viridiscutellata labelled ‘Type M. Goetghebuer’ in RBINS is missing the hypopygium, but NMW contains two well preserved specimens mentioned in the original publication (in which no type was selected). One of these is here designated lectotype to stabilize nomenclature. The other NMW and RBINS specimens become paralectotypes. M. viridiscutellata is conspecific with M. pallidula .

The slide labelled ‘Type M. Goetghebuer’ of Micropsectra franzi contains one body, but two male hypopygia. These are judged to be conspecific, and a lectotype designation is not attempted. The species is conspecific with, and here regarded as a junior synonym of, M. pallidula .

We examined the holotype of Micropsectra candida , and found it to be conspecific with M. pallidula .

Many works treating M. bidentata (e.g. Brundin, 1949; Dittmar, 1955; Pinder, 1978; Langton, 1991; Klink & Moller Pillot, 2003; Langton & Visser, 2003; Ekrem & Willassen, 2004) are apparently based on the hitherto common concept of the species or on the mislabelled ‘ Type M. Goetghebuer’ specimen from Bullange, and thus can be regarded as describing features of M. pallidula . A discussion of the type and taxonomic status of M. bidentata is given under M. atrofasciata (above).

Micropsectra pallidula is very similar to M. aristata in the immature stages (see the remarks on M. aristata above for observed differences). It has been recorded from springs, streams and small lakes throughout Europe.

Figures

Figure 14. Micropsectra pallidula. A, hypopygium. B, superior, median and inferior volsellae. C, median volsella. D, pupal thorax. E, pupal frontal apotome. F, pupal abdominal segments II–VI, dorsal. G, pupal abdominal segments VIII-IX. H, posterolateral combs of pupal segment VIII. I, larval antenna. J, larval mentum, ventomental plates and setae submenti. K, postoccipital plate of larval head capsule.

Figure 15. Paralectotype of Micropsectra pallidula, maxillary palp.