Skusella freemani Harrison 2002
Creators: name: Cranston, Peter S.
name: Tang, Hongqu
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Chironomidae
Skusella
Skusella freemani

description: Skusella freemani Harrison, 2002
(Figs 2 A –C, 3E, 5C)
Material examined. 1♂, Cameroon, Adamawa [Kamerun, Adamaoŭa], 20 km S. Minim, 03.iv.1979 (Nagel & Flacke) (ZSM). 1 Pe / ♀, Nigeria, Anambra State, Opi Lake 1 (= Ogelube Lake), 6°45'0"N 7°29'30"E, 10– 13.xii.1978, reared (Hare) (NHM).
Material mapped, not examined: SOUTH AFRICA: Northern Province, Molopo Oog, Malmani Oog.
Description (data from Harrison in []). Adult male (n = 1) total length 3.4 mm [5.5], wing length 1.9 mm [2.7].
Head. 4 temporals, 11 clypeals. Antennae missing [13 flagellomeres, A.R. 1.5]. Palp lengths (2–5): 38, 100, 100, 88 [45, 189, 201, 330].
Thorax. With single weak scutal hump. Setation: 1 L. aps, 5–6 [11] dc, 3 pa [3], 11 scts [6].
Wing basally infuscate with 2 broad transverse brown bands near contiguous in cells r1, r2+3, and m1+2 with paler ‘windows’ in cells r4+5 and m3+4. Vein setal counts R 17 [26], R1 17 [25], R4+5 13 [34]. 2–4 squamals. V.R. 1.05.
Legs yellow except distal femur and apex of tibia (‘knees’) on all legs brown, on forelegs distal apex of tibia also darkened. Fore and midleg tarsomeres missing. On both mid and hind tibia one comb with curved spur, the other bare.
Hypopygium (Figs. 2 A –C). Tergite IX with 3 [0] anal setae. Anal point swollen, bulbous apically [rounded on holotype, more pointed on paratype]. Superior volsella strongly curved (almost hooked) medially, bearing two strong inner setae. Median volsella 30 long with simple and more taeniate setae up to 20 long (combined MV + apical taenia 50 long). Gonostylus narrowed from midpoint [moderately narrow]. Gcx 120, Gst 122, H.R. 2.8.
Adult female (n = 1) (Harrison in []). Body length c. 3.5 mm [4.4]. Wing length 1.9 mm [2.6].
Head 9–10 temporals, 14 clypeals. Antenna 110, 70, 70, 60, 150; AR 0.42 [0.44]. Palp 2–5: 40, 220, 220, 310 [60, 45, 192, 207, 315].
Thorax. With double scutal hump, the anterior larger than longer, shallower posterior. Setation: 1 L. aps [1], 10 dc [15], 3 pa [3], 3 scts 10].
Wing. As in male, but fainter, with two broad separate darker bands each extending full width of wing. Vein setal counts R 23 [26], R1 21 [27], R4+5 33+ [52]. Squama damaged/missing [6].
All legs damaged but darker ‘femoral-tibial junction (‘knees’) visible on all legs.
Genitalia as in Harrison 2002. Differences from S. pallidipes: seminal vesicles more ovoid, 90 long, maximum width 60, neck weak, less delimited from ducts, ducts initially directed posteriorly then making a complete loop anterior to opening (Fig. 3E, as in Harrison 2002: fig. 29).
Pupa (n = 1). Length 5.3 mm. Pale with darker mid-brown apophyses and golden ‘comb’. Cephalic area with tubercles (c. 40 µm long) bearing c 30µm frontal setae, each recessed in pit. Thoracic setation and thoracic horn structure not recognisable. Prealar tubercle present.
Abdomen. Spinulation on all tergites reduced with respect to S. subvittata: on TII small triangular posteromedian area anterior to very short hook row (of 20 hooks, extending 20% width of tergite), spinule patches on TIII–VI narrower and sparser than in S. subvittata, TVII and TVIII essentially bare (Fig. 5C). Pedes spurii B well developed. Sternites I–VII bare, with anteromedian patch of fine spinules on VIII. ‘Comb’ on posterolateral corner of VIII with 10–11 subequal-lengthed teeth very similar to that of S. subvittata (Fig. 4H). Anal lobe fringe of 110 +/- uniserial taeniae.
Larva. Unknown/unassociated, but see Skusella sp. ‘Opi’ below.
Comments. The adult male from Cameroon was recognized as an undescribed species of Skusella by the late Dr Friedrich Reiss of the Zoologische Staatssammlung München (Reiss in litt. to Cranston, 1989). Earlier a female reared from a pupa by Landis Hare had been identified provisionally as S. pallidipes: here we recognise this to be Skusella freemani Harrison (2002). This second African species of Skusella was described without reference to specimens now available to us. The earlier misidentification may have been due to overclearing and/or bleaching making the wing markings very faint and the characteristic leg banding indistinct.
As recognized by Harrison (2002), Skusella freemani shares the patterned wing with its Afrotropical congener S. pallidipes. However it is differentiated by the banded femora and tibia, a setose squama, the shape and orientation of the superior volsella (curved and directed medially rather than posteriorly (Fig. 2B) and tapered gonostylus (Fig. 2 A) in the male genitalia and in a looped seminal duct in the female genitalia (Fig. 3E). The Cameroon location is some 5,000 km from the type locality in Northern Province of South Africa, and the Nigerian locality even more distant. As might be expected, some variation is seen but may derive from size as South African specimens are significantly larger than those from West Africa. The conservative approach adopted here is to consider these conspecific until further evidence is available.
The associated pupa from Nigeria, described here for the first time, resembles that of S. subvittata and new forms from China in that the fringe extends from the posterior corner of pleura III through to apex of VIII. Differentiation includes the reduced spinulation on the tergites and, uniquely, an absence of spinules on the bare TVII and VIII.
description: Published as part of Cranston, Peter S. & Tang, Hongqu, 2018, Skusella Freeman (Diptera: Chironomidae): new species, immature stages from Africa, Asia and Australia, and expanded distributions, pp. 41-65 in Zootaxa 4450 (1) on pages 51-53, DOI: 10.11646/zootaxa.4450.1.3, http://zenodo.org/record/1444592