Micropsectra aristata, PINDER, 1976

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 : 178-182

MICROPSECTRA ARISTATA PINDER

Micropsectra aristata Pinder, 1976: 275 . Holotype £ ( BMNH 236301 ) England, Dorset, East Stoke, Tadnoll Brook , 30.x.1974, L. C. V. Pinder; 11 paratypes: 1£ as holotype; 1£, 3$$, 3 L & 3 Pex as holotype, except 12.xii.1973 [all examined].

Micropsectra sp. A . ( Pinder, 1974).

Additional material examined

1$ & 2 Pex as holotype, except 19–20.xii.1973; 3££ as holotype, except River Frome , 21.xi.1973 (all ZSM) .

Diagnostic characters

Micropsectra aristata can be separated from other species in the atrofasciata group by the following combination of characters: Adult male with short, triangular digitus; median volsella with straight, parallel-sided

Parameter appendica aristata atrofasciata bavarica klinki (n = 1) logani

Total length [mm] 4.5–5.4, 4.9 4.7–5.1, 4.9 3.8–4.8, 4.2 3.4–3.9, 3.6 Abdomen length [mm] 3.5–4.2, 3.8 3.6–4.1, 3.9 2.9–3.8, 3.2 2.5–3.0, 2.8

Frontal seta length 36–90, 69 108–151, 133 110–154, 127 125–160, 124 Cephalic tubercle length 25–36, 32 12–20, 17 18–25, 21 30–35, 33

Thoracic horn length; width 324–410, 363; 40– 342–396, 358; 47–54, 266–414, 329; 29– 275–350, 301; 35– 50,45 49 36,31 50,39

Thoracic horn chaetae length 158–216, 179 212–270, 243 94–144, 120 90–125, 112 Anterior precorneal seta length 76–94, 86 83–108, 97 115–140, 130 80–125, 101

Median precorneal seta length 72–101, 90 108–126, 121 72–108, 92 65–80, 72

Posterior precorneal seta length 126–162, 139 119–162, 143 126–169, 150 115–150, 129 Prealar tubercle length 12–15 10 30–36, 34 5–10, 6

Median antepronotal seta length 79–126, 107 115–198, 152 97–144, 122 65–105, 87

Lateral antepronotal seta length 61–72, 68 43–94, 67 54–101, 84 40–85, 59

Dc 1; Dc 2 length 43–79, 58; 29–61, 61–101, 77; 18–43, 32 54–90, 79; 40–50, 46 85–125, 103; 70–80, 49 74

Dc 3; Dc 4 length 54–101, 85; 65– 108–137, 120; 97– 83–108, 103; 89– 60–85, 74; 60–85, 71 108; 88 126, 112 126, 103

Hook row width 235–325, 275 252–331, 293 234–342, 268 240–260, 250 Spine/spinule patch TIII length 216–288, 238 180–270, 227 180–252, 207 200–250, 225 Spine/spinule patch TIV length 252–342, 299 288–371, 337 270–360, 299 200–275, 240 Spinule patch TV length 252–324, 292 295–360, 336 270–360, 299 225–275, 245 Spinule patch TVI length 252–324, 289 270–360, 325 144–342, 212 200–275, 240

Spine length TIII 65–79, 71 22–32, 25 50–72, 60 30–40, 32

Spine length TIV 58–65, 59 14–18, 16 54–72, 61 15–20, 18

Spinule length TV 7–11, 9 11–14, 12 8–22, 15 15–20, 16

Spinule length TVI 4 4–7, 5 4 10

Lateral comb SegVIII width 22–25, 23 25–29, 27 18–36, 26 30–40, 35

No. apical teeth on comb 5 3–4 3–5, 4 3–5, 4

No. taeniae in anal fringe 35–42, 38 41–48 18–38, 26 23–35, 30

Male genital sac length 353–360 (2) 342–360, 348 (3) 299–378, 321 275–300, 283 (3)

Female genital sac length 144–162, 154 (3) 169–180 (2) – 110–125 (2)

4.9

3.8

112

54

420; 47

154

101

86

122

7

101

50

65; 50

–; 90

288

202

334

320

234

50

14

11

4

22

4

27–37 ( Klink, 1982)

328

– 3.8–5.1, 4.1 2.9–4.4, 3.2 79–133, 103 12–18, 16 324–684, 462;

22–36, 27 108–144, 129 90–108, 99 126–180, 143 130–180, 150 18–36, 27 108–126, 113 75–101, 84 65–101, 79;

65–83, 74 75–130, 103;

75–115, 101 238–360, 267 162–234, 191 252–360, 252 191–353, 259 76–198, 127 58–72, 62 50–72, 58 8–32, 17 4 29–32, 30 4–5 25–35, 28

274–353, 311 (3)

137–144 (2) lamellae with aristate tips (not spoon-shaped), stem of volsella not reaching margin of superior volsella. Pupa c. 4.9 mm long, with short cephalic tubercles; thoracic horn short with comparatively long chaetae on distal 2/3; prealar tubercle weak or absent; tergite III with spinules (22–32 µm long) in long, posterolaterally curved patches, spinules and points in patches on tergite IV, also in the longitudinal, lateral extensions; points in patches on tergite V; shagreen in patches on tergite VI; large, oval, median patches of shagreen on tergite VII; patches on tergite VI of equal length to patches on tergites IV–VI; microtrichia present between spine patches on tergite III; dorsolateral comb of segment VII narrow with 3–4 separated teeth, middle tooth usually longer. Larva with large, digitiform spur on antennal pedestal; comparatively high AR (c. 2.4) and LOR (c. 6); labral seta SII and some chaetae pectinate, other chaetae plumose, clypeal seta S3 branched; MVR about 0.83.

Description

Adult male. Measurements and ratios in Table 1.

Coloration. Head brownish, pedicels and eyes dark brown. Ground colour of thorax and abdomen greenish; mesonotal stripes, postnotum, preepisternum, median and anepisternum dark brown; legs brown; halteres white; abdomen somewhat darker apically. Pinder (1976) reported some specimens to be lighter in colour.

Head. Antenna with 13 flagellomeres, longest seta longer that terminal flagellomere. Frontal tubercles minute (4–7 µm); most temporal setae in 1 row, inner verticals sometimes in 2 rows.

Wing. Subcosta and media bare, 2–4 long setae on brachiolum, squama bare.

Legs. Pulvilli small, about 1/3 length of claws. Fore tibia with small scale, spur c. 35 µm long; mid and hind tibial combs c. 20–25 µm long; mid ta 1 with 4–5 sensilla chaetica.

Hypopygium ( Pinder, 1976: figs 1–3). Anal tergite rather triangulate, with separate, posteriorly directed anal tergite bands; 5–7 median tergite setae placed on an elevated hump anterior to anal point base; 11–20 ventral apical setae. Anal point relatively broad, slightly triangular, without knob at posterior end of high parallel crests; large microtrichia free area at base of anal point. Superior volsella roundish with 6– 8 dorsal and 3–4 median setae on setiger, 1 strong seta on stem; small field of dorsal microtrichia on stem and ventrally on setiger. Digitus small, triangular, not reaching margin of superior volsella. Median volsella comparatively short and stout with setiform, and simple, parallel-sided lamellae with aristate tips; stem reaching half length of setiger of superior volsella. Inferior volsella with small dorsoapical swelling bearing numerous posteriorly directed setae. Inner margin of gonocoxite with 3 strong setae.

Pupa. Coloration: pupal exuviae brownish with darker brown thorax, apodemes, lateral and posterior margin of TVIII and anal lobe. Pinder (1976) reported the abdomen of alcohol preserved specimens to be green. Measurements in Table 2.

Cephalothorax ( Fig. 6A, B ). Cephalic tubercle present, small; pedicel sheath tubercle very weakly developed. Thoracic horn fairly short with numerous very long chaetae on distal 2/3; precorneals arranged in triangular pattern, the 2 anteriormost setae situated closer to each other than to the third, anterior precorneal shorter than other two, posterior precorneal usually longest; 1 median antepronotal, 2 lateral antepronotals (1 sensillum basiconicum); 2 pairs of dorsocentrals, anterior pair shorter and weaker than posterior pair, Dc 2 shorter than Dc 1, Dc 3 and Dc 4 equally strong. Granulation in a small field dorsally along median suture on scutum. Prealar tubercle very weak; nose of wing sheath weak.

Abdomen ( Pinder, 1976: fig.7). TII with shagreen in triangular, median patch with anterolateral extensions, oval shagreen-free patch posteromedially; pedes spurii B on segment II obvious; hook row about half as long as segment width. Spinules of TIII in large, laterally curved patches on posterior half of tergite, shagreen extensively distributed laterally and anterior to spinule patches as well as in between. Patches of TIV consisting of spinules in anterior, oval patches with longitudinal, lateral extensions; shagreen present laterally to anterior and longitudinal patches. Patches of TV similar to those of TIV in shape and composition, somewhat shorter. Patches of TVI similar to those of TIV and TV in shape and size, or rather oval, consisting only of shagreen. TVII with large, oval, median, longitudinal patches of shagreen; TVIII with weak anterolateral patches of shagreen. Segment I with 3 D setae; segment II with 3 D, 4 V, 3 L; segment III with 5 D, 4 V, 2 L, 1 lateral taenia; segment IV with 5 D, 4 V, 0–1L, 2–3 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 5D, 4V, 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 strong O-setae present anteriorly on sternites II–VIII. Anal lobe with evenly, strongly convex lateral margins, fringe with about 450–550 µm long taeniae in 1 row. Posterolateral comb of segment VIII narrow, with median teeth longer than lateral teeth.

Larva (4th instar, n = 4). Head capsule well sclerotized and dark brown. Live individuals reported to be orange green in colour ( Pinder, 1976), uniformly yellow when preserved in alcohol. Total length c. 6.0 mm. Measurements and ratios in Table 3.

Head ( Pinder, 1976: figs 8–13). AR about 2.5; antennal pedestal with c. 36 µm long, 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 pedestals; LOR c. 5.3–6.0; SII pectinate; chaetae plumose, pectinate, simple; chaetulae simple; S3 branched with middle branch very long ( Fig. 6C ). Mentum with weakly developed lateral notches on somewhat pale median tooth; ventromental plates more strongly curved laterally, with obvious striation along whole length; premandible with 2 robust teeth, inner tooth broader, brush well developed; mandible pecten mandibularis slightly convex; postoccipital plate broad.

Body. Anterior prolegs with long, simple spines; posterior prolegs with c. 50 simple hooks in two rows; L2 simple; anal segment with 4 anal tubules; supraanal seta c. 115 µm long; procercus with one short and one long (c. 90 µm) dorsal seta, with 6 short and 2 long anal setae.

Remarks

Micropsectra aristata has been recorded from several contries in Europe ( Saether & Spies, 2004), but we have only examined material from rivers and streams in Dorset, England. The species is well figured by Pin- der (1976), and we only present a few additional drawings here.

Micropsectra aristata is very similar to M. pallidula in the immature stages. Pupae of the former species can be recognized by being larger, having shorter cephalic tubercles, longer antepronotals, and shorter spinulae in the spine patches of tergite III. The larvae of M. aristata can be separated only by having a shorter spur on the antennal pedestal, a shorter antennal pedestal and a lower LOR.

Figures

Figure 6. Micropsectra aristata. A, pupal thorax. B, pupal frontal apotome. C, clypeal seta S3 of larva.