Griffiths' Treatment of the Genera of Anthomyiidae in the Nearctic Region Part 3: The Pegoplata-Group

Griffiths covered this group in volumes 5-6 of his work, which were published in 1986 and 1987, respecitvely.

1. Genus Pegoplata

Griffiths' notes:
"The genus is the first of a group of genera included by Hennig (1976a: lxiii) in the "Nupedia-group" (here called Pegoplata-group in view of the synonymy of Nupedia with Pegoplata), characterized primarily by the modified structure of the distal section of the aedeagus (expanded, rather uniformly sclerotized without separation of paraphalli from dorsal sclerotization, adorned with pairs of papillae, with acrophallus well developed as separate sclerite in midventral position). The processus longi are retained, and Hennig suggests that the presence of a basal projection on the gonostylus (where it articulates with the processus longus) may be an additional constitutive character of this group...The aedeagal structure validates the core of Hennig's Pegoplata-group containing in his treatment the genera Pegoplata, Nupedia, Myopina, Enneastigma, and Calythea. Another common character of the Pegoplata-group (= Nupedia-group) in this sense is the enlargement of (at least) the female palpi, which probably represents a constitutive synapomorphy although species with enlarged female palpi also occur in a few other genera (such as Paradelia). When apical setulae are present on the scutellum they are very fine, not stouter than the fine ventral setulae...the apical setulae are also very fine in Myopina and Calythea.
...I amalgamate Pegoplata and Nupedia (= Pegomyia virginea and P. dissecta groups of Huckett 1941), since I can find no consitutive modifications (autapomorphies) characteristic of Nupedia alone...
Unlike in Myopina, strong sexual dimorphism in eye size and frons width is normally retained in Pegoplata; only in P. abnormis (Stein) is a male form with rather widely separated eyes brown. The interfrontal setae are normally well-developed in both sexes, tending to be displaced forwards rather than reduced in males with closely approximated eyes.
The prosternum and the hypopleuron are bare, and the notopleural depression normally lacks setulae additional to the usual two long setae in all species of Pegoplata; the scutellum is finely pubescent apically and ventrally, bearing the usual two long marginal pairs of setae and a shorter discal pair. The hind tibiae lack an apical pv seta. The pulvilli are sexually dimorphic, enlarged to a varying degree in males but always small (less than half as long as the 5th tarsal article) in females.

...The male 5th sternite is flat and more or less heart-shaped (with convex outer margins), with dense inner fields of short setulae or spinules...
...The only species of Pegoplata whose life-history has been studied in detail is P. aestiva (Meigen), whose larvae feed in faeces. Information for other species is sketchy or in need of confirmation...
...In the Nearctic Region species of Pegoplata can be found in a wide range of habitats from hot desert to the alpine and low arctic zones."

Characterization tables:
Griffiths did not recognize subgenera for Pegoplata, despite containing the former genus Nupedia, because he believed the subdivisions of the genus required more study. One characterization is provided. Four sections were recognized: the P. palposa section, P. infirma section, P. acutipennis section, and the P. cuticornis section, with the Palearctic P. debilis superspecies as incertae sedis. The photographic characters used are the length of the mentum, development of a keel between the antennae on the face, projection of the lower facial margin, number of rows of the postocular setulae of males, pubescence of the arista, and ventral costal chaetotaxy. Only the P. (section infirma) aestiva superspecies has the mentum elongated and a swollen keel on the face between the antennae. In other species, the mentum is short and the facial keel is absent or narrow. Most species have a lower facial not projecting beyond the level of the parafrontal angle except for the P. aestiva superspecies and P. (section cuticornis) nasuta with an ambiguous state for species P. cuticornis. The number of rows of dorsal postocular setulae on the male is varied across the genus. They are present in 2-3 rows in the P. aestiva superspecies, P. infirma, P. (section infirma) tundrica, P. nasuta, and an ambiguous state for P. cuticornis. The P. palposa superspecies and P. (section palposa) pictipes have a plumose arista, whilst other species have an arista with only short pubescence. The species in the P. palposa section have the lower surface of the costa extensively setulose, with ambiguous states for the P. (section acutipennis) acutipennis superspecies, P. (section acutipennis) abnormis superspecies, and P. valentinae.

My comments:
This poorly known genus has about 10 species occurring in our area. Fortunately, the genus can be somewhat recognizable if certain features are paid attention to. The third antennal segment is 1.4-2.5 times as long as wide. The prementum is finely dusted to shining, and the palpi of at least the female are enlarged apically. Palpi can be difficult to see and judge in photos, but Griffiths has referred to palps expanding distally as expanding to "two thirds the width of third antennal article" for a species of Myopina. Scutellum with ventral hairs present. Proepisternum with or without setulae. Thorax with 3(-4?) postsutural dorsocentral setae. Anterior post-sutural supra-alar or prealar seta in most species short or absent. Presutural acrostichal setae usually in widely separated rows. Griffiths did not provide information about the anepisternum for this genus, but P. palposa may lack an anterodorsal seta here. Chaetotaxy of the anepisternum was not considered in descriptions until next one or two volumes, although alas it is probably one of the most distinguishing and photographable characters in the family. Scutellum mostly bare dorsally to largely setulose. Mid tibia usually without av exclusive of apical setae. Hind tibia usually with 2 pd, the apical pd seta conspicuously longer than the other, without any pv setae in both sexes.
The Manual of Nearctic Diptera does not treat this genus well. Pegoplata aestiva was outdatedly placed under the genus Paregle in couplet 13. Some sources have suggested Pegoplata aestiva may have four post-sutural dorsocentral setae, but I have not been able to remember which. Longest aristal hairs may at most be as long as the antennae are wide (in P. palposa superspecies and P. pictipes). The mid tibia of only P. aestiva may have a mid av seta, keying it to couplet 34's "Adia". Going to couplet 35 for species without the av and 2 pd (or less) on the hind tibiae, the species of Pegoplata with a setulose ventral costal surface are difficult to place, as these species will have interfrontal setae present, although perhaps short in the males. Separating Pegoplata from Pegomya can be tricky and may require species by species separation, looking at acrostichal arrangement, numbers of posthumeral setae, color, and presence of interfrontal setae where useful. Otherwise, remaining species will key to Nupedia with the prementum being "pruinose". This is mostly true with most species having a "finely dusted" prementum instead of entirely shining per Griffiths, however, P. infirma and P. tundrica are two exceptions of "Nupedia" with a rather shining to shining prementum. Furthermore, Pegoplata juvenilis can have up to 4 posterodorsal setae on the hind tibiae in the female. This keys it all the way to Paraprosalpia (=Alliopsis) in couplet 67, where the apical setulae, if present, are weak, but differs by the finely dusted and not polished prementum, the long aristal pubescence, and probably a few other characters, such as lack of setulae behind the vibrissal prominence (like for Pegomya vs Eutrichota). Alliopsis is a difficult to define genus but made up of distinctive groups of species that are usually easily eliminated from options when compared to species of Pegoplata.

2. Genus Myopina

Griffiths' Notes:
"This small Holarctic genus was placed in the Pegoplata-group by Hennig (1976a) on account of the presence of papillae on the distal section of the aedeagus and the nature of the articulation between the gonostylus and the processus longus. This opinion is accepted here, although the male genitalia are so extraordinarily modified...that it will be difficult to have confidence in the placement of the genus unless species with less modified structure are discovered. The earlier concepts of Fucelliinae or Myopinini, in which Myopina was included by earlier authors...were unnatural mixtures, as Hennig says.
The previously described valid species belonging in Myopina are three only: M. myopina (Fallen), M. scoparia (Zetterstedt), and M. crassipalpis Ringdahl. I here add one new species , M. martini n. sp...
Species of Myopina will be recognized by the following combination of characters: The head structure (Fig. 834) is not sexually dimorphic, with the relatively small oval eyes equally widely separated in both species; crossed interfrontal setae are always present; additional post-ocular setulae are present dorsally below the marginal row; the third article of the arista is thickened on its basal third to half; the palpi are somewhat expanded distally at least in females.
The male abdomen is swollen (more or less circular in cross-section)...
...The thoracic chaetotaxy is in no way unusual in Myopina, and in particular the fine ventral setulae of the scutellum are present as in most other Anthomyiidae. Huckett's (1965a, 1971a) characterization of "Myopinini" with the phrase "scutellum usually without hairs on ventral surface" did not apply to Myopina. The propleural depression and hypopleuron are bare, and the notopleural depression lacks setulae additional to the usual two long setae in all species. The scutellum bears the usual two long marginal pairs of setae and a shorter discal pair; its apical setulae, when present, are short and fine (not stouter than ventral setulae). The lower squama is weakly expanded or linear. The hind tibiae lack an apical pv seta. The legs are strongly sexually dimorphic, displaying unusual modifications (varying according to species) in the males.

Species of Myopina are not commonly collected and their immature stages are unknown...unique synapomorphies of the males of [M. scoparia and M. crassipalpis] are the presence of a complex ventral sclerite between synsternite (6+7) and the hypandrium...and the presence of a tuft or brush of setae on the posterior surface of f3."

Characterization tables:

My comments:
This small genus of distinctive flies are so unusual for the family that they would probably be identified no further than Calyptratae or even mistaken as an oestroid family if wing venation is ignored. Nonetheless, very few identified representatives are known, but images of some Myopina myopina can be found readily online. In addition to Griffiths' characterization, these flies also have very wide gena, the prementum finely dusted to shining, scutellum broadly bare centrally, crossvein dm-cu usually straight, at most slighty bent, ventral surface of the costa usually bare, at most with submarginal row of fine setulae, and legs dark. The prosternum in only M. martini is setulose. Two of the four species, M. myopina and M. scoparia, have the scape and pedicel yellowish. Males of 3 species are known, excepting M. martini. They exhibit much sexual dimorphism in the legs, with M. myopina males having a bowed first hind tarsomere, and other species differing from females by at least a slightly swollen hind femur and at least the hind tarsi shortened. The male of M. martini is unknown but would be the missing key to understanding the relationships of these species to each other.

3. Genus Calythea

Griffiths' notes:
" The above synonymy follows Ackland (1968) and Hennig (1968), and has been adequately discussed in Ackland's paper. In North American literature, only the names of Calythea and Anthomyiella have been used...It is possible that Enneastigma (Stein, 1916: 122), containing three species from southern Europe, can also be included in Calythea...
...In comparison with Pegoplata and Myopina, Calythea (and Enneastigma) stand out as apomorphous (derived) with respect to the reduced vestiture of the gonostylus...
...Calythea is more diverse in the Old World than the New (represented in the Afrotropical and Oriental, as well as Palearctic, regions). Only five species occur in the Nearctic region. Four of these are evidently very closely related (showing the same characteristic setulosity of the hypopleuron and identical genitalia), belonging to what I propose to call the C. micropteryx superspecies. Since the Neotropical C. comis (Stein) also belongs to this superspecies, we are probably dealing with the results of a Tertiary invasion of the New World. The most northern member of this superspecies, C. bidentata (Malloch), retains a Holarctic distribution. The fifth Nearctic species (not belonging to the C. micropteryx superspecies) is the holarctic C. pratincola (Panzer)...
...The Nearctic species of Calythea are all small flies (less than 5 mm wing length), easily confused with small muscids or fanniids on superficial inspection on account of the enlarged lower squama (larger in area than upper) and distally faint anal vein. They can be readily recognized (in both sexes) by their possession of bright silvery grey-dusting on the abdomen , forming a contrasting pattern with opaque sooty areas (Fig. 862). As in other members of the Pegoplata-group, interfrontal setulae are retained in all females and most males (with the exception of C. pratincola), the female palpi are (at least slightly) expanded and the scutellum retains ventral setulae (with apical setulae, when present, very fine, not stouter than the ventral setulae). The normal sexual dimorphism in eye size and frons width is retained. The thoracic chaetotaxy varies between species, providing many diagnostic characters; among the sclerites described in this work only the propleural depression is bare in all species (hence omitted from the species descriptions); the scutellum bears the usual two long marginal pairs of setae and a shorter discal pair. The hind tibiae lack an apical pv seta. The pulvilli are only weakly dimorphic (not much longer in males than in females)...
...The larvae of two species of Calythea, C. micropteryx (Thomson), and the Palearctic C. nigricans (Robineau-Desvoidy), are known to feed in mammalian feces."

Characterization tables:

My comments:
These small flies belong to a complex of various calyptrate flies across families that show sometimes contrasting patterns of black and silvery white dusting that can be very easily confused for each other. Species in Limnophora, Gymnodia/Brontaea, Anthomyia, some tachinids, and probably some more I am forgetting. It is important to keep in mind wing venation, leg chaetotaxy, presence or absence of interfrontal setae, maybe the elongated basiventral seta on the base of the hind first tarsomere, maybe some color details, and maybe dorsocentral setae when trying to determine these genera from each other. The anal vein won't be of much help as this genus has it rather faint distally. There are only 4 species known north of Mexico with one additional species from Mexico included in Griffiths' treatment. They are relatively homogenous in structure except for color, variations, and minor chaetotaxy, so it can be described further here.
Prementum finely pruinose, thorax mainly black with silvery areas in the males, but varying from densely dusted with black patches in C. pratincola to almost entirely dark in C. crenata, more dusted in females and with coppery sheen, abdomen with dark and light areas, more densely dusted in females, legs dark, wings slightly yellowish tinged to brownish tinged.
Male eyes narrowly separated, no wider than width of anterior ocellus, eyes pilose only in the Mexican species C. crenata, gena below lowest point of eye nearly eliminated (extremely narrow) except for 0.1-0.15 times eye height in C. pratincola, peristomal/lower facial margin scarcely to strongly projecting anteriorly beyong parafrontal angle, face with (C. monticola) or without a shining ocellar tubercle separating antennal bases, with or without a keel betwen antennae, various in width and height, interfrontal setulae short or absent in males of C. pratincola only, well-developed in other forms, genal setae in 1-2 rows, not described to have setulae behind the vibrissal prominence, postocular setulae usually in 1 row dorsally, only known in the female of C. pratincola to be in 2 rows, third antennal article 1.6-1.8 times as long as wide, arista with short to very short pubescence, palpi not expanded to distinctly expanded distally to about width of third antennal article, wider in females, mentum 0.3-0.6 times as long as head height.
3 pairs of presutural acrostichals usually in widely separated rows at least anteriorly, rather narrowly in some C. bidentata, with or without additional setulae in between, 1 anterior and 2 strong posterior posthumeral setae, notopleuron with setulae anteriorly or bare, prealar short or absent, scutellum bare dorsally, largely bare in C. pratincola, katepisternal setae largely arranged 1+2, with anterior seta potentially short or reduced in the female of C. pratincola, prosternum and hypopleuron setulose (at least laterally and anteriorly, respectively) in all species except C. pratincola.
Costal spinules of wing all shorter than costal width, lower surface of the costa bare. Crossvein dm-cu almost straight.
Mid femora without distal anterior or anteroventral setae. Fore tibia with 0-1 ad (if present, long), 0-1 p; mid tibia with 0-1 ad, 0-1 pd, 0-2 p; hind tibia with 1-2 av, 1-2 ad, 1-2 pd, the latter very long if only one present.

Evenhuis, N.L. & Pape, T. (editors). 2022. Systema Dipterorum, Version 3.9., accessed on 4 August 2022.
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Publicado por aispinsects aispinsects, 25 de noviembre de 2022


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