Myiodoriops Townsend, 1935

Inclan, Diego J. & Stireman, John O., 2014, A new species and synonymy of the Neotropical Eucelatoria Townsend and redescription of Myiodoriops Townsend, ZooKeys 464, pp. 63-97 : 77-79

Taxon classification Animalia Diptera Tachinidae

Myiodoriops Townsend, 1935

Myiodoriops Townsend, 1935: 227. Type species: Myiodoriops marginalis Townsend, 1935: 227, by original designation. Guimarães 1971: 141 (catalog); Wood 1985: 39-40 (redescription, as junior synonym of Erythromelana ); Wood and Zumbado 2011: 1403 (key to Central American genera, as junior synonym of Erythromelana ); Inclán and Stireman 2013 (revision of Erythromelana , with Myiodoriops marginalis Townsend as revived status).

Included species.

Myiodoriops marginalis Townsend, 1935.

Diagnosis.

Myiodoriops can be separated from other blondeliine genera (see discussion section below) using a combination of external characters and traits of the male terminalia including: 2 katepisternal bristles, 2 postpronotal setae (or, if a small inner seta is present, all three arranged in a line or broad arc), sparsely haired eyes, facial ridge with hairs on lower 1/3 or less, vein M ending in R4+5 vein just before wing margin or in wing margin very close to R4+5, lack of proclinate orbital setae in males, the mid-dorsal depression extending nearly to the hind margin of tg1+2, absence of a piercing structure in females, and short, spine-like setae on the anteriorly on the apex of the surstyli.

Myiodoriops is superficially similar to the Eucelatoria obumbrata species group and to the genus Erythromelana in size, shape, and general appearance, which may explain the former grouping of these taxa into a single genus. However, it can be separated from these taxa using external morphological traits. It differs from the genus Eucelatoria generally in lacking the apomorphic piercing structure and associated short spines on ventral margins of abdominal tergites in females and absence of median discal setae on abdominal tergites 3 and 4, and it specifically lacks the apomorphic traits of the Eucelatoria obumbrata group of R4+5 bristled nearly to crossvein r-m and sex patches in the male. Myiodoriops can be separated from Erythromelana by having the vibrissa inserted slightly above the lower facial margin (subtended by one or more setae), vein M ending in R4+5 vein or in wing margin very close to R4+5, and the mid-dorsal depression extending nearly to the hind margin of tg1+2. Additionally, Myiodoriops has only 2 katepisternal setae, which differs from Eucelatoria and from most species of Erythromelana which have 3 (see Inclán and Stireman 2013). The male terminalia are also distinct from these other blondeliine taxa, particularly with respect to the surstylus, which is anteriorly curved and narrowed towards its tip with spine-like setae on the anterior side of its apex. Furthermore, males in this genus have the pregonite strongly curved anteriorly, which differs from the rectilinear one of Erythromelana .

The presence of short spines on the tip of the surstylus is reminiscent of Myiopharus (see Wood 1985; O’Hara 2007), which Myiodoriops resembles in a number of other respects. However, it appears distinct from the former genus in lacking proclinate orbital setae in the male, possessing bristles on the lower 1/3 of the facial ridge or less, an apparent lack of ommatrichia, three reclinate orbital setae in males, 2 postpronotal setae, or if 3, the innermost reduced in size and all 3 arranged in a broad arc, relatively short, stout surstylus and cercus, and a small and nearly pointed postgonite (see discussion section below).

Redescription.

Redescribed from 5 males (including the type Myiodoriops marginalis ) and 6 females.

Length: males, 5.1-5.8 mm (x = 5.42 mm); females, 3.9-5.1 mm (x = 4.54 mm).

Head: Parafacial covered with dull silver pruinescence. Fronto-orbital fig and vertex black in ground color, covered with silver pruinescence appearing grayish from certain angles, usually with faint sparsely golden pruinescence dorsally. Frontal vitta usually entirely black, sometimes fading to dark-brown toward antenna. Pedicel black and first flagellomere black, covered with fine microtrichia and appearing grayish. Arista long, with minute setae, black with brown on basal 1/3 or less, thickened on basal 1/4 or less. Fronto-orbital fig with 5-7 medioclinate frontal setae in male, 4-7 in female; 3 reclinate inner orbital setae in males, 2 in females; female with 2 proclinate outer orbital setae, male without outer orbitals. Vertex with one reclinate inner and usually one lateroclinate outer vertical seta, the latter often barely or undifferentiated from the row of postocular setae in both sexes. Inner orbital and vertical setae usually about twice the length of frontal setae. Ocellar setae well-developed, proclinate. Parafacial bare and narrow with the narrowest point about equal to the widest portion of the palpus in males; in females narrower, about the basal width of the palpus. Facial ridge with hairs on basal 1/3 or less, and lower margin of face descending slightly below the level of vibrissa. Subvibrissal ridge short, usually with 1 to 3 setae; postgena narrow, with a distinct but small genal dilation. Posteroventral part of the head with the majority of white-yellowish fine setae and posterodorsal part of the head with one row of black setae behind the postocular row. Palpus brownish to black in color, distinctly swollen apically, more markedly in females.

Thorax: Shiny black in ground color; presutural scutum with evident white pruinescence, postsutural scutum with much sparser pruinescence revealing underlying black ground color. In dorsal view, only the presutural scutum appears grayish; whereas in lateral view the postsutural scutum appears grayish as well. Faint white pruinose stripes on presutural scutum leaving 4 black vittae; the inner 2 vittae longer and thinner, almost 1/2 the width of each of the outer 2 vittae. Prosternum with several hair-like setae. Postpronotum with 2 or 3 setae, when 3, the inner most is reduced in size and together they form a broadly obtuse angle, ca. 130-150°. Proepisternum bare. Katepisternum with 2 setae. The first postsutural supra-alar seta smaller than the notopleural setae. Scutellum with 3 pairs of setae, without apical setae or with one small hair-like pair.

Legs entirely black. Tarsal claws longer than 5th tarsomere in male and shorter than 5th tarsomere in female. Mid tibia with 2 posterodorsal setae, and 1 ventral seta. Hind tibia with anterodorsal setae uneven in length and not closely spaced; 2 well-developed posterodorsal setae, rarely with 1 additional shorter seta; 2 anteroventral setae. Upper and lower calypters translucent yellow-brownish. Wing length nearly equal to body length. Wing usually hyaline, rarely light fumose on the anterior edge. Wing vein R4+5 dorsally setose only at its base, and R1 bare. Vein M smoothly curved at bend and ending in vein R4+5 near the wing margin or separately in the margin closely approximated to vein R4+5.

Abdomen: Mostly black with yellow laterally on tg1+2 to tg4 on males, fully black in females. Transverse bands of sparse white pruinosity usually on the anterior 1/4 of tg1+2 to tg5. Mid-dorsal depression of tg1+2 extending to marginal setae and nearly to hind margin. One pair of median marginal setae on tg1+2 and tg3; a row of median marginals on tg3 to tg5; 1 pair of lateral marginal setae on tg1+2 and tg5; discal setae absent in both sexes. Sternites completely overlapped by tergites.

Male terminalia: Sternite 5 with median cleft smoothly V-shaped; apical lobes narrowed to broad points at their apices. The anterior margin of st5 clearly concave. The basal section of st5 distinctly shorter than the length of the apical lobes. Hypandrial arms separated. Pregonite curved anteriorly and tapered to a narrow rounded tip. Postgonite distinctively curved anteriorly, with narrow, almost pointed apex. Epiphallus small, hidden between the pregonites. Surstylus, in lateral view, broad, anteriorly curved and narrowed toward the apex, considerably longer than cercus. Surstylus with several short spine-like setae on the anterior side of its apex. Cercus, in lateral view, broad, slightly concave along anterior margin and narrowed only on the posterior margin of the apex. In posterior view, the cerci with long rectilinear upper lobes, nearly as long as the medial section + apical cleft combined. Apices of cerci, in posterior view, with excavated inner margins. Lateral margins of cerci without a constriction towards the apical section; apical cleft well defined. Distiphallus divided at base into long and a broader sclerotized portion with a toothed margin anteriorly.

Geographic distribution and seasonal occurrence.

See the distribution of Myiodoriops marginalis below, except for four undescribed specimens (see discussion below) that were collected in Brazil, Peru and Argentina (Fig. 12). All known specimens were collected at lower elevations (<200 m) except one specimen collected in Peru at 1600 m. Specimens have been collected from January until October, but most of the material was collected in January.

Discussion.

The phylogenetic affinities of Myiodoriops marginalis are unclear. As indicated in the diagnosis, there is little reason to believe that the species belongs with its former congeners in the genus Erythromelana or Eucelatoria , nor does it appear to be closely related to these taxa (see also Inclán and Stireman 2013). Myiodoriops marginalis is morphologically similar to the large and difficult genus Lixophaga , but it lacks the enlarged pair of bristles on sternite 5 characteristic of males of this genus (although it does have a number of smaller bristles; Fig. 14c) and the postpronotal bristles of Myiodoriops marginalis , if three, are arranged in a line. It even more closely resembles members of Euthelyconychia in general appearance and chaetotaxy, sharing with this genus some features of the male genitalia as well (e.g. surstylar and postgonite shape), but the cerci are differently shaped and Euthelyconychia appears to lack surstylar spines. The possession of the unusual, anteriorly directed surstylar spines, suggests a close relationship with Myiopharus , and it is possible that Myiodoriops marginalis represents a highly autapomorphic species of this genus, or of Euthelyconychia . Without detailed systematic study and analysis of these genera and the Blondeliini as a whole, which is beyond the scope of the present study, these possibilities cannot be confirmed or refuted. Therefore, we retain Myiodoriops marginalis in its originally described genus.

The genus description is based primarily on the specimens available for the known species Myiodoriops marginalis . However, we found four specimens from Peru, Brazil and Argentina that belong to this genus, but they appear represent one or more undescribed species near Myiodoriops marginalis . We have included these specimens in the genus description to cover all the generic variability, but we did not describe these specimens given the limited material and their poor condition. Additionally, of these four specimens, three are females and each is from a different locality. These four specimens exhibit slight differences in external morphology (e.g., parafacial width and abdominal coloration), but it is unclear if these differences represent intraspecific variation, male-female dimorphism, or actual differences between species. Therefore, we leave these specimens undescribed until additional material is available that can be used to help establish their identity.