Myopella Malloch, 1934

Michelsen, Verner, 2023, A reassessment of the Andean genus Myopella Malloch (Diptera: Anthomyiidae), Zootaxa 5336 (3), pp. 413-423 : 414

Genus Myopella Malloch, 1934

Myopella Malloch, 1934: 196 . Type species: Myopina appendiculata Stein, 1904 , by original designation.

Myopinella Michelsen, 2010: 1273 , syn. nov. Unnecessary new replacement name for Myopella Malloch (see following note).

Nomenclatorial note. Malloch (1934) proposed the name Myopella in Muscidae (now Anthomyiidae ), thereby overlooking the earlier homonymous use of the name in Conopidae by Robineau-Desvoidy (1853). This homonomy was mentioned by Pont & Ackland (2009: 9), but no action taken. Accordingly, in my key to the Neotropical genera of Anthomyiidae ( Michelsen 2010: 1273) , I proposed the new replacement name Myopinella for the preoccupied name Myopella Malloch. This was unfortunate, as I subsequently realized (cf. Evenhuis et al. 2010: 113) that the name Myopella Robineau-Desvoidy by a ruling of the Commission (Opinion 1870) had been placed on the Official Index of Rejected and Invalid Generic Names in Zoology ( ICZN 1997: 133), evidently for reasons other than Malloch’s homonymous use of the name. Accordingly, the name Myopella Malloch, 1934 is re-instated herewith.

Redescription. Small (wing length 3.0– 4.8mm), wholly black anthomyiid flies ( Figs 1A–C ) with dark pruinosity leaving no shine on facial parts of head and no dark pattern on dorsum of thorax and abdomen.Arista short, thickened basally, very short-pubescent. Mouthparts unremarkable with small, bicuspid prestomal teeth. One presutural pair of acrostichals stronger than prescutellar pair. Prealar seta very short, slightly spinose, surrounded by 2–3 similar, but finer spinules. Prosternum with strong marginal setulae. Vein C bare ventrally (excluding slightly ventrally displaced setulae from the lower anterior spinule-setula row). Upper calypter small, wider than long, lower calypter reduced to a narrow strip, concave at hind margin. Inner hind margin of hind coxa forming a conspicuous (males) or short (females) angular process. Fore tibia with 2 long d setae; mid tibia with 1–2 av–v, 2 ad, 2 pd setae; hind tibia with 3–4 av, 3 ad and 3 long and a variable number of short pd setae. Male legs, especially fore femur, stout; all tarsi shorter than respective tibiae; distal tarsomeres wider than and as long as combined length of two preceding tarsomeres. Male abdomen: sternite I setulose; tergite III latero-ventrally expanded compared to adjacent tergites; sternites II–IV extremely modified with apodemal lateral extensions ( Figs 2A, B ). Male terminalia ( Figs 3A–E , 4A– E ): sternite V large, posterior lobes long and slender, richly setose; tergite VI bare, fused together with pregenital sclerite; articulation between surstyli and the epandrium mediated by an intercalary sclerite; bacilliform sclerites absent; surstyli without usual anthomyiid subapical incision but with a row of 3–4 short denticles medio-ventrally; pregonites short, with single apical seta; postgonites short, with antero-basal seta and a few sensilla; phallus with short distiphallus bearing a simple, sheet-like acrophallus. Female abdomen ( Figs 5A, B ): sternite I bare; segment V extended, 1.5–2 times as long as segment IV; posterior margin of tergite V with a pair of dorso-lateral membranous incisions leaving three flexible sclerotized flaps that, together with a similar flap from sternite V, help to seal the tip of segment V after full retraction of the ovipositor. Ovipositor ( Figs 6A–D ): sternites VI and VII only maintained on posterior part of each segment; segment VIII without dorsal hind marginal setae/setulae; epiproct much wider than long, with two unequal pairs of setulae; hypoproct small, smooth and slender with 2(–3) tiny setulae; cerci helmetshaped, smooth sclerites with short setulae and a few sensilla arising from enlarged alveoles; spermathecae oblong, somewhat irregular in shape; ducts very slender on distal part.

Distribution. The genus with only two known species has been found exclusively under the harsh, cool temperate conditions of the Central and South Andes, ranging from 4030m asl in Peru to sea level on Tierra del Fuego ( Fig. 7 ). The known South Andean range of Myopella angustifrons coincides with that of M. appendiculata . The only species found at very high altitudes in the Central Andes is M. appendiculata . The reason might be that the fully feminized (broad-fronted) male head makes it better adjusted for a living in wind-stroken and barren habitats.

Biology. Unknown apart from what can be inferred from the morphology of the adult flies. The pronounced feminization of the male head in Myopella appendiculata indicates an adjustment to “terrestrial” rather than “aerial” courtship behavior necessitated by a living in open, windy habitats (alpine meadows, littoral zones). Other adjustments to a “terrestrial” life found in both species of Myopella are the stout legs with short, robust tarsi and abundant setae. The strongly modified venter of the male abdomen may also play a role in courtship behavior (release of sex pheromones?). The flaps at the hind margin of the female segment V effectively seal the entrance to the fully retracted soft-cuticular ovipositor, a possible means to reduce water loss in dry periods. The long, soft ovipositor with short cerci suggests that oviposition takes place within some kind of decaying organic matter in which larval development takes place.

Figures

FIGURE 1. Myopella angustifrons Malloch (A, B), M. appendiculata (Stein) (C), males. Habitus (A); head, dorso-lateral view (B, C). Same scale for B and C.

FIGURE 2. Myopella appendiculata (Stein) (A), M. angustifrons Malloch (B), males. Sternites II–V (A); sternites I–V (B). Same scale for A and B.

FIGURE 3. Myopella angustifrons Malloch, male terminalia. Hypopygium, lateral (A), and caudal (B); pre- and postgonite (C); phallus (D); sternite V (E). Same scale. Setae omitted on epandrium in A and B.

FIGURE 4. Myopella appendiculata (Stein), male terminalia. Hypopygium, lateral (A), and caudal (B); pre- and postgonite (C); phallus (D); sternite V (E). Same scale. Setae omitted on epandrium in A and B.

FIGURE 5. Myopella appendiculata (Stein), female abdomen. Tergites I–V (A); sternites I–V (B). Same scale.

FIGURE 6. Myopella appendiculata (Stein) (A, B), M. angustifrons (Malloch) (C, D), females. Ovipositor, flat mounted (A, C); spermathecae (B, D). Same scale for A, B and D.

FIGURE7. KnownrecordsofMyopella angustifronsMalloch (blackdots) andM.appendiculata(Stein) (bluedots)superimposed on a map of South America.