Centrioncus prodiopsis Speiser, 1910

Feijen, Hans R. & Feijen, Cobi, 2023, A revision of Centrioncus Speiser (Diptera, Diopsidae, Centrioncinae) with descriptions of new species from Angola, Burundi, and Kenya, ZooKeys 1144, pp. 1-93 : 1

Centrioncus prodiopsis Speiser

Figs 8 , 29 , 139-145 , 146-149 , 150, 151 , 152

Centrioncus prodiopsis Speiser, 1910: 191; Hennig in litt. 1950 (Shillito archive, NHMUK); Feijen 1983: 80; De Meyer 2004: 28.

Type series.

Tanzania, lectotype ♂ (designated by Feijen 1983), Kibonoto [Kibongoto 3°11'S, 37°06'E], Kilimandjaro [Kilimanjaro], 7.x.1905-06, 2000-3500 m, Y. Sjöstedt (NHRS). Paralectotypes: 1 ♀, same locality, 5.i.1905-06, 2000 m, Y. Sjöstedt (NHRS); 1 ♀ (no abdomen), same locality, ix.1905-06, 1300-1900 m, Y. Sjöstedt (NHRS); 1 ♂ (no abdomen, but genitalia drawn by Hennig prior to1950, who marked the drawings with "holotype C. prodiopsis "), same locality, 5.i.1905-06, 2000 m, Y. Sjöstedt (ZMHB).

Material studied.

Kenya: 2 ♀, Rift Valley Prov. , Olloitokitok [Oloitokitok], malaise trap, indigenous forest, 2.94456°S, 37.50714°E, 11-25.xi.2011, 1853 m, R. Copeland (ICIPE) .

Diagnosis.

Centrioncus prodiopsis can be recognised by mesally slightly depressed pruinose frons with two glossy spots; glossy collar; pruinose, blackish brown scutum, brown humeral calli; blackish brown scutellum with brown lateral sides; blackish brown pleura, brown propleuron with paler ventral half; scutellar spine/scutellum ratio: ~ 0.98; apical seta/scutellar spine ratio: ~ 1.02; pale, strongly incrassate fore femur (l/w ratio: 2.92) with ~ 31.1 tubercles, on inner side with brown stripe on distal two-fifths (Fig. 143 ); very large central wing spot (Fig. 8 ), covering nearly basal half of cell r4+5, extending into distal half of cell br, extending into distal two-thirds of cell bm+dm and well into cells r2+3, m1 and m4; tergites 1-6 uniformly blackish brown; female 7th spiracle in tergite; sternite 4 rounded, anteriorly significant, rounded invagination; sternite 5 rounded trapezoidal, anteriorly significant, rounded invagination; sternites 4 and 5 with anterior pair of small heavily sclerotised spots (Fig. 146 ); sternite 5 half-length of sternite 4; sternite 6 trapezoidal, 1.4 × as broad as sternites 1-5; anterior sclerite of sternite 7 trapezoidal, w/l ratio: ~ 2.5, posterior sclerite of sternite 7 rounded, broad U-shaped (Figs 147 , 148 ); female cercus rather elongate, l/w ratio: 4.0; subanal plate pentagonal, laterally convex and with acuminate apex; smooth spermathecae, very large apical dimple, cup-shaped, some dispersed tiny tubercles; common base of outer and median arms of surstylus short, broad; outer arm trapezoidal, straight lateral sides, broadening apically to twice width at base, apically with row of 17 tubercles (Fig. 150 ); median arm slender, parallel-sided, slightly curved rod, shorter than outer arm, apically with six setulae, no spinous setae; outer arm and basal half of median arm clothed in microtrichia on outer side; inner arm short, ca. half-length of other arms, with bulbous preapical apophysis; subepandrial clasper elongate, narrow, hardly constricted at base, apical corners rounded, apically hardly convex (Fig. 151 ); male cercus basally narrow, broadening apically, with broad lateral extension.

Supplementary description.

Feijen (1983) studied the ♂ lectotype and one ♀ paralectotype. The redescription by Hennig (in litt.) of the specimen of the type series in ZMHB also became available. Now two additional females from Kenya could be examined, but one of these two flies was rather teneral. Updated biometrical data are now given. Additional morphological data and illustrations are presented.

Measurements. Speiser (1910) provided length for type series as 4¾-5¼ mm. Length of body 5.9 mm (♀ paralectotype), 4.9 mm (Kenya ♀) and 5.0 mm (♂ lectotype), width of head 1.20 mm (♀ paralectotype), 1.08 and 1.04 (Kenya ♀♀), and 1.06 mm (♂ lectotype), length of wing 5.4 mm (♀ paralectotype), 4.5 mm (Kenya ♀) and 4.6 mm (♂ lectotype), length of scutellar spine 0.37 mm (♀ paralectotype), 0.34 and 0.36 (Kenya ♀♀), and 0.29 mm (♂ lectotype).

Head. As in lectotype and paralectotype, Kenya specimens with frons slightly depressed mesally, anterior quarter of pruinose frons less dark brown and on either side of ocellar tubercle with glossy spot (Fig. 141 ); length of outer vertical seta 0.31 mm (n = 2), length of fronto-orbital seta 0.22 mm (n = 2).

Thorax. Collar dark brown, mainly glossy; basiliform prosternum dark brown, slender, triangular and anteriorly acuminate; scutum blackish brown and pruinose, humeral callus brown and more glossy (Figs 139-141 ), Speiser (1910) stated humeral callus dark mahogany red, but was not visible in Feijen (1983); scutellum blackish brown, pruinose, lateral sides and spines brown (Figs 139 , 140 ); colouration of pleura of Kenya specimens corresponds to description of lectotype and paralectotype by Feijen (1983), especially more brownish propleuron with paler ventral half (Fig. 139 ); densely pruinose spot on katepisternum (also mentioned by Speiser) distinct (Fig. 139 ); basiliform prosternum dark brown, slender, triangular and anteriorly acuminate; scutellar spine/scutellum ratio: 0.98 (n = 2, range 0.97-1.00); scutellar spine/body length ratio: 0.069 (n = 1); two Kenya specimens with apical seta/scutellar spine ratio: 1.02 (range 1.00-1.04) [ Feijen (1983) described apical seta as "slightly larger than spine"]; scutellar length/scutellar width (at base) ratio: 0.64.

Wing. Almost transparent with very large, distinct, brownish central spot covering nearly basal half of cell r4+5 (well past crossvein dm-m), extending into distal half of cell br and extending into distal two-thirds of cell bm+dm and well into cells r2+3, m1 and m4 (Fig. 8 ); vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line; vein M4 continuing distal of crossvein dm-m in almost straight line to wing margin; cell cua subtriangular (Fig. 8 ).

Legs. Femur 1 (Fig. 143 ) strongly incrassate, l/w ratio: 2.92 (n = 1); two rows of spinous setae on distal two-thirds of femur 1 with 7.3 ± 0.2 setae (n = 8), inner row with 3.9 ± 0.1 setae, outer row with 3.4 ± 0.2 setae; two rows of tubercles on distal three-quarters of femur 1 with 31.1 ± 0.6 tubercles (n = 8), inner row with 15.4 ± 0.3 tubercles, outer row with 15.8 ± 0.4 tubercles; femur 1 yellowish brown with on inner side brown stripe on distal two-fifths (Fig. 143 ); femur 3 (Fig. 145 ) distally with 3.9 ± 0.4 (n = 8) tubercles; setal formula 3.4, 3.9, 15.8, 15.4, 3.9 which agrees with formula of type-series as given by Feijen (1983): 3.5, 3.8, 15.8, 14.3, 3.0; femur 3 yellowish with on outer side brown stripe on distal quarter and on inner side vague brown spot apically (Figs 144 , 145 ).

Preabdomen. Tergites uniformly blackish brown (Fig. 142 ), almost glossy, laterally with some pruinosity (Fig. 139 ); sternites brownish (Fig. 139 ); sternite 1 glossy but laterally with some pruinosity, sternite 2 glossy, sternites 3-6 pruinose (Fig. 146 ); membranous ventral areas with dark lateral spots; sternite 1 trapezoidal, anteriorly broader (Fig. 146 ); intersternite 1-2 dark, laterally acuminate, with thin lateral connections to main sternite 2; sternite 3 rectangular with rounded corners; sternites 4 and 5 anteriorly rounded, with significant rounded invagination, both sternites with pair of small heavily sclerotised spots anteriorly (Fig. 146 ); sternite 5 half-length of sternite 4; sternite 6 broadening posteriorly, ~ 1.4 × as broad as sternites 1-5, with convex lateral sides.

Female postabdomen. Tergite 7 brown, paler brown along posterior margin (Fig. 149 ); anterior sclerite of sternite 7 trapezoidal, narrowing posteriorly, w/l ratio: ~ 2.5 (Figs 147 , 148 , Table 8 ), brown but paler along posterior margin, glossy on anterior two-thirds, pruinose on posterior one-third; posterior sclerite of sternite 7 rounded, broadly U-shaped (Figs 147 , 148 ), clothed in microtrichia and with 4-6 setulae at both posterior apices; cercus (Fig. 149 ) rather elongate, l/w ratio: 4.0 (Table 8 ); 7th spiracle at edge of tergite (Fig. 148 ).

Male postabdomen. Outer and median arms of surstylus well separated, with short, broad common base (Fig. 150 ); outer arm somewhat trapezoidal with straight lateral sides, broadening apically to almost twice width at base, apically with row of 17 tubercles with tiny setulae in between, with rectangular, raised section with 11 setulae basally on inner side (Fig. 150 ), outer arm wholly clothed with microtrichia on outer side; median arm slender, parallel-sided, slightly curved rod-shaped, slightly shorter than outer arm, apically with 4 small setulae and 2 long setulae, no spinous setae present, basal half of outer side covered with microtrichia; inner arm of surstylus short, ca. half-length of other two arms, with a bulbous preapical apophysis, apically with five setulae (Fig. 150 ); subepandrial clasper (Fig. 151 ) elongate, slightly constricted at base, narrow, somewhat rectangular, apically with rounded corners, apical edge slightly convex, glabrous, with three long setulae centrally on inner side and four small hairs at apical edge; cercus basally narrow, broadening apically, with short, broad lateral extension, length/greatest width ratio: 1.4 (Table 8 ); ejaculatory apodeme + sac very large, 12% of body length (Table 9 ).

Distribution and habitat.

The collecting localities are shown on the map for Eastern Africa (Fig. 29 ). The type locality is on the southern side of the Kilimanjaro region, while the Kenyan specimens are from the northern side of the Kilimanjaro region. In a straight line, the distance between the two localities is 55 km.

Remarks.

Speiser (1910) based his description on two pairs of specimens. Feijen (1983) used for his redescription one pair from NHRS. In the NHRS collection, there was one additional fly without an abdomen, while ZMHB also housed one fly without an abdomen. Feijen designated the ♂ of the pair studied as lectotype and the ♀ as paralectotype. Now, a typed letter from W. Hennig, dated 3.xii.1947, was recovered from the J.F. Shillito archive (NHMUK). The section relevant to Centrioncus ran as follows:

Ueber den Holotypus von Centrioncus prodiopsis Speiser, der sich in der Sammlung des Zoologischen Museums Berlin befindet, habe ich mir früher einmal, für den Fall, dass er zerstört werden sollte, Notizen gemacht. Kopien meiner Zeichnungen fuge ich für Sie diesem Briefe bei. Sie können diese Zeichnungen beliebig verwenden. Auch gegen Veröffentlichung habe ich nichts einzuwenden, da wir hier doch in absehbare Zeit nicht dazu kommen.

Ueber die systematische Stellung von Centrioncus prodiopsis habe ich mir noch kein abschliessendes Urteil gebildet. Ich weiss nur sicher, dass die Art nicht zu den Sepsiden, und auch nicht zu den Megamerinidae gehört. Gegen Ihre Ansicht, dass es sich um eine Diopside handelt, wäre von der morphologie des Kopulationsapparates her wohl kaum etwas einzuwenden. Da ich selbst aber die Verwandtschaftsgruppen um die Sapromyzidae noch nicht genügend untersucht habe, möchte ich mit meinem Urteil vorläufig zurückhalten. Von Kopfborsten sind nur 1 Vertikalborste und 1 Frontorbitalborste vorhanden, von Thorakalborsten 1 Notopleuralborste (die hintere), 1 Supraalar- und 1 Postalarborste.

[In a brief translation this comes to: Regarding the holotype of Centrioncus prodiopsis in ZMHB, I made years ago notes in case it would be destroyed. I enclose copies of the drawings I made. If you like, you can use these for publication. I have not yet formed a conclusive judgment on the systematic position of Centrioncus prodiopsis . I only know for sure that the species does not belong to the Sepsidae or Megamerinidae . In view of the morphology of the copulation apparatus, there would hardly be anything to object to your view that it is a diopsid. However, I would like to reserve my judgment for the time being. On the Centrioncus head 1 vertical seta and 1 fronto-orbital seta are present, while the thorax counts 1 notopleural seta (the posterior one), 1 supra-alar seta and 1 postalar seta.]

From this letter, it became obvious that the fly without abdomen in ZMHB is a male, so the fly without abdomen in NHRS has to be a female. Hennig indicated the ZMHB fly as the holotype. However, Speiser did not designate a holotype. All four specimens of the type series were labelled as syntypes ( Feijen 1983). It seems likely that Hennig was not aware of the three NHRS flies. As such, the designation of the lectotype by Feijen (1983) remains valid. Hennig’s drawings of the ZMHB fly showed that this male was definitely conspecific with the lectotype. As, since the type series of 1905-1906, male specimens of C. prodiopsis have apparently never been collected again, it is considered useful to copy Hennig’s drawing of the male postabdomen (Fig. 152 ) as an addition to Feijen’s (1983) drawings and for historical reasons. In this drawing, Hennig’s original labels are indicated. The ZMHB specimen is now designated as male paralectotype.

Lonsdale (2013), in a review of Tanypezidae and Strongylophthalmyiidae , includes for the phylogenetic analysis in the character matrix as out-group representatives for the Diopsidae Sphyracephala subbifasciata Fitch and Centrioncus prodiopsis . However, the origin of the single Centrioncus studied was not given, though for the genitalia character states, Feijen (1983) was used. The two specimens from Kenya were, after 106 years, the first C. prodiopsis collected since the type series. Literature references to additional C. prodiopsis records related to other Centrioncus species or to Teloglabrus species ( Feijen 1983).

Figures

Figure 29. Distribution map of the seven Eastern African Centrioncus species.

Figure 152. Centrioncus prodiopsis, ♂, abdomen segments 5 - 8, epandrium and surstylus, lateral view. This is a (restored) drawing made by Willi Hennig in the late 1930 s. Hennig was probably not aware of the three ZMHB specimens and assumed the NHRS specimen to be the holotype. The NHRS specimen is now designated as paralectotype.

Figures 5 - 8. Centrioncus, dorsal view of wings 5 ♀, holotype, C. crassifemur sp. nov., N'dalatando 6 ♂, C. decoronotus Njuki-Ini Forest 7 ♂, C. jacobae Mount Soche 8 ♀, C. prodiopsis, Oloitokitok. Scale bars: 0.5 mm.

Figures 139 - 145. Centrioncus prodiopsis, ♀, Oloitokitok 139 habitus, lateral view 140 thorax, dorsal view 141 head, anterolateral view 142 abdomen, dorsal view 143 fore femur, inner view 144 hind femur, outer view 145 hind femur, inner view. Scale bars: 0.5 mm (139 - 142); thorax, head, abdomen), 0.2 mm (143 - 145).

Figures 146 - 149. Centrioncus prodiopsis, ♀, Oloitokitok 146 sternites 1 - 6, ventral view 147, 148 sternite 7, ventral view 149 tergite 7 and cerci, posterolateral view. Scale bars: 0.5 mm (146); 0.1 mm (147 - 149).

Figures 150, 151. Centrioncus prodiopsis, ♂, lectotype, Kibongoto 150 surstylus, inner view 151 subepandrial clasper and base of surstylus, posterior view. Scale bars: 0.1 mm.