Aphromyia stuckenbergi Courtney

Courtney, Gregory W., 2015, A new genus and species of net-winged midge from Madagascar (Diptera: Blephariceridae: Blepharicerinae), Zootaxa 4052 (1), pp. 107-116 : 110-115

Aphromyia stuckenbergi Courtney , new species

Diagnosis. Larva (instar IV): as given for genus. Pupa: as given for genus. Adult male ( Figs. 13–15 ): Tergite X produced posteriorly as bilobed cerci, each broadly rectangular, intercercal area comprised of wide U-shaped notch. Inner gonocoxal lobe S-shaped, glabrous. Gonostylus simple. Dorsal paramere with bilobed posteroventral margin; posterior lobe sinuous, ribbon-like, arching dorsally, then anteriorly to broadly triangular, sclerotized apex. Adult female: Sternite VIII bilobate, medial depression U-shaped. Sternite IX (genital fork) broadly Y-shaped. Hypogynial valves elongate, parallel, slightly rounded apically. Spermathecae three in number, lateral corpora ovoid, slightly longer than wide, medial corpora pyriform, larger than others, all with short necks; ducts short, tenuous and unpigmented.

Description. Larva ( Figs. 1–3 , 7–9 ). Measurements, instar IV (N=4): total length 4.25 mm (3.65–4.80), width 2.42 mm (1.95–2.85), cranial width 0.82 mm (0.80–0.85).

Overall shape onisciform, markedly compressed dorsoventrally, abdominal divisions at least as wide as cephalic division, intercalary segments poorly developed, anal division broadly semicircular. Cranial sclerites rugose, dark brown medially, contrasting light to dark brown laterally; ecdysial sutures with short stem line (<0.05 mm), posterior margin of frontoclypeal apotome extending nearly to posterior cranial margin. Clypeal shield well developed. Post-cranial part of cephalic division, trunk segments, anal division uniformly brown; prolegs light brown dorsally. Cephalic division (i.e., abdominal tergite I), abdominal tergites II–VI each with two, darkened, slightly raised ridges extending across midline, length approximately ¼ width of division; abdominal tergites II–V and anal division each with dark, thickened ridge along anterior margin. Prolegs simple, unpaired. Anal division broadly semicircular, with scattered rugosity posteromedially; posterior margin flattened, rimlike, with few short setiform sensilla along margin. Chaetotaxy: Cephalic division posterolaterally with fanshaped or obovoid setae; substernal sensilla not apparent; primary- and secondary trunk sensilla reduced; abdominal segments, anal division medially mostly glabrous, laterally with fan-shaped or obovoid setae, setae opaque in color. Prolegs with scattered setiform sensilla, increasing in length distally, apex with cluster of approximately 6–10 setiform sensilla, glabrous ventrally; posterior prolegs (VIIth) on anal division each minute, with one prominent setiform sensilla apically, 2– 3 smaller setiform sensilla marginally. Gill with five filaments, posterior two much longer than anterior three.

Pupa ( Figs. 4–6 , 10 ). Measurements: ♂ (N = 2): length 4.15 mm (4.10–4.20), width 2.8 mm (2.75–2.85); ♀ (N = 4): length 4.55 mm (4.50–4.60), width 2.96 mm (2.90–3.05); respiratory organ length (anterior lamella, both sexes) 1.14 mm (1.10–1.15).

Overall shape broad, oval. Cephalic sclerite broadly triangular. Respiratory organ with four lamellae, closely bunched at anterior edge of pupa; lamellae prominent, erect, elongate, tapering to acute point apically, converging medially; outer lamellae heavily sclerotized, dark brown, inner lamellae lightly sclerotized, pale. Proboscis theca short, not extending beyond base of foreleg sheath. Integument: Cephalic sclerite glabrous; branchial sclerite set with numerous papillae laterally and anterior to respiratory organ; alar sclerite dorsally with abundant papillae; mesotergite dorsally with papillae posterior to respiratory organ, laterally glabrous; metatergite and abdominal tergites uniformly set with broad, flattened, dorsal papillae; papillae dark brown, set with numerous minute spicules; abdominal tergites laterally with numerous grooves, oriented obliquely parallel to tergite margin; anal tergite glabrous posteriorly. Ventrolateral adhesive discs on each of abdominal segments IV–VI.

Male: Measurements (N=3): Total length 3.03 mm (3.00–3.10), wing length 4.83 mm (4.75–4.90), width 1.77 mm (1.75–1.80).

Head ( Fig. 11 ): Structure: Eyes dichoptic, broadly separated dorsally, interocular distance approximately 0.5 mm; 35–40 rows of ommatidia, along mid-meridian; ommotrichia, short. Clypeus length/width = 1.0. Proboscis short (0.2 mm), free portion approximately 0.3 X head width; mandibles absent; galea short, length less than that of maxillary palpus; maxillary palpus with two segments, proportions 1:3. Antenna with 12 flagellomeres; flagellomeres light brown, cylindrical in shape, ultimate flagellomere 1.4 x length of penultimate flagellomere; scape with prominent setiform sensilla apically, pedicel with prominent setiform sensilla medially and apically, both otherwise mostly glabrous; flagellomeres with numerous, small, uniformly distributed sensilla. Facial chaetotaxy: Setiform sensilla groups as follows (number per side): clypeals (10–12), parietals (6–9), occipitals (4– 6).

Thorax and Appendages: Wing ( Fig. 12 ): costal vein terminating in radial sector; reduced subcostal vein; radial sector with three veins, R4+5 forked; medial sector with single vein, M1; anal lobe prominent but lacking anal vein. Legs: Tibial spurs 0–0–1, spur length 0.22 mm (0.21–0.24). Leg-segment proportions: foreleg— 28:35:18:8:5:3:3, midleg—34:32:22:7:5:4:4, hind leg—37:35:15:5:3:2:2. Tarsal claws without hooks. Chaetotaxy: Thorax glabrous except for diffuse row of 3–6 setiform sensilla on posterior margin of anepisternum; scutellum with numerous setiform sensilla laterally grouped at posterolateral corner (N≈10) and along margin; coxae with 4– 6 prominent setiform sensilla.

Coloration: Frons, face and clypeus dark brown. Thorax pruinose. Mesoscutum and scutellum dark brown; pleuron silvery brown dorsally, dark brown ventrally. Legs light brown. Halter light brown stem base, otherwise dark brown. Abdominal tergites uniformly dark brown.

Terminalia ( Figs. 13–15 ): Epandrium (tergite IX) moderately sclerotized, subquadrate, simple, emarginate posteromedially; setiform sensilla more numerous along posterior, lateral margins. Tergite X produced posteriorly as bilobed cerci, each with broadly rectangular apex; intercercal area consisting of a wide U-shaped notch; setiform sensilla restricted to posterior margin. Gonocoxites subrectangular, broadly fused with hypandrium (sternite IX) ventrolaterally, with few setiform sensilla laterally; inner gonocoxal lobes heavily sclerotized, dark brown, lobe Sshaped, glabrous, expanded to spoon-shaped apex. Gonostylus simple, expanding slightly toward apex, truncated apically, set with numerous setiform sensilla on dorsal and inner margins. Dorsal paramere with sinuous, ribbonlike sclerite laterally, curving dorsally to broadly triangular, sclerotized apex with bilobed posteroventral margin; posterior lobe sinuous, ribbon-like, arching dorsally, then anteriorly to broadly triangular, sclerotized apex. Ventral paramere slightly longer than aedeagal rods, lightly sclerotized, elongate, tapered to blunt point apically, encircling aedeagal rods.

Female: Similar to male. Measurements (N=2 [but both specimens incomplete]): Total length 5.00 mm, wing length 5.50 mm, width 2.00 mm.

Thorax and Appendages: Legs: Tibial spurs 0–0–1, spur length 0.22 mm. Leg-segment proportions: foreleg— 27:39:15:6:5:4:4, midleg—36:33:12:5:4:3:6, hind leg—35:32:19:5:3:2:3.

Terminalia: Sternite VIII bilobate, medial depression U-shaped. Sternite IX (genital fork) broadly Y-shaped, base of Y thickened, branches markedly tapered, curved laterad toward apex. Hypogynial broad basally, narrowed slightly to base of apical valves; valves elongate, parallel, somewhat concave medially, slightly rounded apically. With three spermathecae; lateral corpora ovoid, slightly longer than wide, medial corpora pear-shaped, all with short necks; ducts short, thin, unpigmented. Chaetotaxy: Sternite VIII with 2–3 setiform sensilla laterally; sternite VII, hypogynial plate with abundant microtrichia; epiproct with 15–20 prominent setiform sensilla apically.

Etymology. Named in honor of the late Dr. Brian Stuckenberg, collector of most type material, avid student of Blephariceridae , and generous colleague and friend.

Type material. Holotype [♂]: “ MADAGASCAR: [Fianarantsoa Province], Ambalavao District, Antanifotsy, [Andringitra National Park], east slopes of Ambaravarandanitra Mountain, Kimoro River, [approx. 22°08.62'S 46°53.44'E, 1680m], 19.i.1958, coll. B.R. Stuckenberg.” Specimen pinned from EtOH with head and terminalia in glycerin microvials. Allotype [♀]: same data as holotype; dissected, but mouthparts, 1 wing and 1 set of legs missing, in EtOH. Paratypes: same data as holotype [15 ♂ (9 pinned, 1 dissected with head and terminalia on slide; 6 in EtOH, 4 dissected with head and/or terminalia on slides), 1 ♀ (EtOH, dissected, head on slide, in glycerin jelly); 3 ♂ pupae (EtOH, 1 dissected with respiratory organ on slide), 4 ♀ pupae (EtOH)]; ”[Fianarantsoa Province, Ambalavao District, Andringitra National Park], Mt Andringitra, Ampatsikahitra, J.M. [coll. J. Millot]” [4 instar IV larvae, in EtOH]. All type material deposited in the Natal Museum.

Distribution. Aphromyia stuckenbergi is currently known only from the Andringitra Massif in southeastern Madagascar. Andringitra, the second highest mountain in Madagascar, is a massive granitic batholith exposed as part of the main southeastern escarpment, where it receives monsoon clouds constantly during the day, afternoon thunderstorms, and heavy evening mists (B.R. Stuckenberg 2001, personal communication).

Bionomics. Given the limited material available for study, it is difficult to generalize about the life history or ecology of A. stuckenbergi . At the time of Stuckenberg’s collections, the type locality apparently was in excellent condition, “a fine waterfall” with “pristine rainforest that covered the eastern slopes of the mountain” (B.R. Stuckenberg, 2006, personal communication). Unfortunately, despite the fact that the waterfall resides within the boundary of Andringritra National Park, the site apparently has changed dramatically since the Stuckenberg collections. Based on a 2007 visit by former students, the riparian zone and surrounding hillsides now consist entirely of grasslands and a few small parcels of secondary forest, with cattle grazing permitted throughout (R.B. Sam & M.J. Petersen, 2007, personal communication). Collection efforts in 2007 failed to record additional specimens of A. stuckenbergi . As of 2007, the area above the falls apparently was intact; therefore, additional sites may exist upstream of the type locality.

Discussion. Ever since larval material was first described by Paulian (1953), the phylogenetic position of this blepharicerid has been an enigma. As the only non-edwardsinine from Madagascar, and characterized by one of the most aberrant larval stages in the entire family, this blepharicerid has been of considerable interest to students of net-winged midges.

Previous attempts to place this species in a phylogenetic framework have been problematic, which at least partly explains why this fly had not yet been described and named (Stuckenberg, 2006, personal communication). Although Paulian and others (e.g., Courtney 2003) considered the immature stages to support possible inclusion in the Apistomyiini, some of the character evidence (e.g., well developed clypeal shield in larvae) may actually define a larger clade including also the paltostomatines. Stuckenberg (2004, and in various subsequent personal communications) suggested the possibility that this unusual Malagasy blepharicerine was instead a member of the Paltostomatini, but acknowledged that colocephaly and mouthpart reduction in both sexes has obscured phylogenetically important characters. Determining the phylogenetic relationships of Aphromyia remains indelibly linked with uncertainty regarding relationships among major subgroups across the Blepharicerinae, especially in the widespread Palearctic / Oriental / Australasian Apistomyiini and the largely Neotropical “Paltostomatini.” Zwick (1981) suggested a sister-group relationship between the Paltostomatini + Apistomyiini and the exclusively northern Blepharicerini , with the former defined by reduced wing venation, structure of the pupal respiratory organs, and modifications of the larval clypeus. Zwick (1977) defined the Apistomyiini by the presence of four pairs of adhesive discs in pupae, while monophyly of a more derived clade within Apistomyiini (i.e., beyond his “ Peritheates + Neocurupira ” clade) was based partly on reduction of the seventh larval pseudopod. Other investigations ( Zwick 1981, 1998; Stuckenberg 2004; Gibson & Courtney 2007) provide additional support for monophyly of the Apistomyiini, with most characters pertaining to structure of the adult labium: labellum enlarged, elongate, and bearing distinct pseudotracheae. Superficially similar (i.e., elongate) labia occur in paltostomatines but, according to Stuckenberg (2004), their structure is quite different (base of labium elongate, while the labellum remains short). A comparable arrangement occurs in a few, relatively derived apistomyines ( Stuckenberg 1970, 2004; Zwick 1998; Gibson & Courtney 2007) but in these taxa the pupa retains a long, empty labial theca ( Stuckenberg 2004). In contrast, the labial theca of pupal Aphromyia is markedly short. Despite the hypothesis presented by Stuckenberg (2004), it is possible that paltastomatines comprise a paraphyletic assemblage from which the Apistomyiini evolved.

There is little doubt that Aphromyia belongs to a clade comprised of all paltostomatines and apistomyines. Larvae provide one of the most compelling characters (presence of clypeal shield) to support such a hypothesis. The body shape (onisciform or chiton-shaped) and/or marginal chaetotaxy (rows of fanshaped or obovoid sensilla) bear resemblance to some apistomyiines (e.g., Nothohoraia , Theischingeria , some Horaia ), as does reduction of the seventh larval pseudopod. However, one or more of these features are also known in certain paltostomatines (unpublished data), suggesting the possibility of convergence. In other characteristics it is difficult to find any phylogenetically informative characters in the highly aberrant larvae.

Aphromyia pupae are in most respects typical of many paltostomatines and apistomyiines, so pupal characters provide few insights into phylogenetic affinities. Each respiratory organ is comprised of four erect lamellae closely bunched at the anterior end of the pupa, with the outer lamellae being heavily sclerotized, elongate, and tapering to a point, and inner lamellae lightly sclerotized, as long as the outer lamellae but not pointed. The latter condition and the general orientation of the outer lamellae (converging medially) are reminiscent of many apistomyines. However, unlike apistomyiines with reduced adult mouthparts, the labellar theca of Aphromyia is short. In this feature Aphromyia is similar to pupae of certain paltastomatines (e.g., Aposonalco ). One of the most compelling pupal features pertains to the number of ventrolateral adhesive discs. Despite past uncertainty about this character, most available specimens clearly possess three pairs (on abdominal segments IV–VI). Specimens previously thought to have a 4th pair (i.e., on abdominal segment III) are immature and somewhat damaged, making details of abdominal segment III difficult to see. The presence of only three pairs of adhesive discs is significant, as this represents the blepharicerid groundplan and distinguishes Aphromyia from many paltostomatines and all Apistomyiini.

The reduced wing venation clearly places Aphromyia in a clade comprising paltostomatines and apistomyines. The relatively elongate hind legs provide another possible synapomorphy, as does reduction of maxillary palpal segments. Unfortunately, many other potentially informative adult characters pertain to the labellum ( Stuckenberg 2004), which is obscured by Aphromyia ’s colocephalous condition and the general reduction of mouthparts. Like other taxa with comparably modified mouthparts (e.g., Hapalothrix Loew and Tianshanella Brodsky ), Aphromyia remains difficult to place in a definitive phylogenetic position. Given its aberrant morphological characters, it is possible that placement of Aphromyia will depend on future collection of fresh material and analyses using molecular markers. This in turn may depend on the discovery of additional populations of this rare fly.

Madagascar is remarkable for the level of endemism (e.g., plants: 89%; mammals: 93%; birds: 58%; reptiles: 96%; amphibians: 99%) and for biotic diversity virtually unmatched by any other biotic region ( Goodman and Benstead 2003). In terms of both endemism and diversity, aquatic arthropods appear to parallel trends seen in other faunal groups ( Elouard and Gibon 2003). Indeed, Madagacar’s blepharicerid fauna exhibits 100% endemism! Unfortunately, it is likely that many of these endemics, including perhaps Aphromyia, could already be extinct because of deforestation in recent decades and concomitant degradation of water quality. The only known locality for Aphromyia, Andringitra National Park, harbors other remarkable endemics (e.g., coleopteran genus Heterogyrus Legros ) and appears to be particularly at risk. It is hoped that description of Aphromyia will draw more attention to the unique biota of this region and prompt greater protection of the streams that remain.

Figures

FIGURES 11 – 15. Adults of Aphromyia stuckenbergi. 11, Male head, frontal view. 12, Male wing. 13, Male terminalia, dorsal view. 14, Male terminalia, transparent dorsal view. 15, Male terminalia (phallic structures), dorsal view. Scale bars = 0.25 mm (Fig. 11), 0.5 mm (Fig. 12), 0.1 mm (Figs. 13 – 15).

FIGURES 1 – 6. Light micrographs of larval and pupal Aphromyia stuckenbergi. 1, Larval habitus, dorsal view. 2, Larval habitus, ventral view. 3, Larval habitus, lateral view. 4, Female pupa, frontal view. 5, Female pupa, dorsal view. 6, Female pupa, ventral view. Scale bars = 1 mm.

FIGURES 7 – 10. Scanning electron micrographs of larval and pupal Aphromyia stuckenbergi. 7, Larval prolegs on abdominal segment IV and V, dorsal view on right side. 8, Larval proleg on abdominal segments V, ventral view. 9, Larval proleg (VII) on anal division, dorsal view on right side. 10, Microsculpture, pupal abdominal tergite III. Scale bars = 200 µm (Fig. 7), 100 µm (Figs. 8, 9), 20 µm (Fig. 10).