Heleomyza serrata (Linnaeus, 1758) (Diptera: Heleomyzidae) is a synanthropic saprophagic fly that ranges across the Holarctic region. Gill (Reference Gill1962) characterised H. serrata as “very common in collections.” However, a new species, Heleomyza captiosa (Gorodkov, 1962), was described from European material determined in collections as H. serrata. Although the two species are externally similar, the male genitalia of H. captiosa are distinct from that of H. serrata.
In the Palaearctic, H. serrata is found in more northern regions (e.g., Sweden, Finland, Mongolia), and H. captiosa is found in central and southern regions (e.g., France, Poland, Italy; Gorodkov Reference Gorodkov, Soós and Papp1984). Gorodkov (Reference Gorodkov1962) hypothesised that the two species may be allopatric, but because H. captiosa specimens have long been identified as H. serrata, the range of each species is not precisely known. Accordingly, Leria domestica Robineau-Desvoidy, 1830, described from Yonne, France, and Helomyza fuscana Meigen, 1838, described from Bavaria, Germany, may be senior synonyms of H. captiosa, but the nomenclature is unresolved (Gorodkov Reference Gorodkov, Soós and Papp1984).
Thus far, only H. serrata, and not H. captiosa, had been recorded from the Nearctic region (Gill Reference Gill1962, Reference Gill, Stone, Sabrosky, Wirth, Foote and Coulson1965). However, on 4 January 2014, a male Heleomyza specimen (Fig. 1) was collected by Lisa Isaacs from decomposing elephant ear plants, Alocasia macrorrhiza (Linnaeus) G. Don (Araceae), in Deane, Letcher County, Kentucky, United States of America, and given to B.D.B. for determination. The specimen keys to Heleomyza serrata in Gill’s (Reference Gill1962) key to Heleomyza, but the elongated shape of the epandrium and basistylus (Fig. 2A) is a poor match for that species. Instead, they are consistent with those of H. captiosa. The specimen will be deposited in the collection of the Ohio State University, Columbus, Ohio, United States of America.
Habitus of male Heleomyza captiosa (Gorodkov) specimen collected in Deane, Kentucky, United States of America.
Comparison of male genital structures of two species of Heleomyza Fallén: A, Heleomyza captiosa (Gorodkov) specimen collected in Deane, Kentucky, United States of America, and B, H. serrata (Linnaeus), modified from Giordani and Vanin (Reference Giordani and Vanin2023). Abbreviations: ep, epandrium; ds, dististylus; bs, basistylus.
To our knowledge, this represents the first Nearctic record of H. captiosa. To aid in identification of this species, we provide a brief diagnosis for H. captiosa and an updated key to Heleomyza of the Nearctic region. Morphological terminology follows Cumming and Wood (Reference Cumming, Wood, Kirk-Spriggs and Sinclair2017), except that we follow Woźnica’s (Reference Woźnica2004, Reference Woźnica2011) treatment of the male genitalia of Heleomyzinae, adopting the term basistylus for the basal genitalic process (“epiphallic process” of Gill (Reference Gill1962); “surstylus” of Gorodkov (Reference Gorodkov1962)), and dististylus for the distal process (“surstylus” of Gill (Reference Gill1962); “editum” of Gorodkov (Reference Gorodkov1962)).
Heleomyza captiosa (Gorodkov, Reference Gorodkov1962)
Leria captiosa Gorodkov Reference Gorodkov1962: p. 663, figs. 34, 35
?Leria domestica Robineau-Desvoidy Reference Robineau-Desvoidy1830: p. 654
?Helomyza fuscana Meigen Reference Meigen1838: p. 369
Diagnosis. Heleomyza captiosa is externally similar to H. serrata, having hyaline wings, one strong katepisternal bristle, a bare anepisternum (rarely with a single setula posteriorly), and a bare anepimeron. The base of the epandrium of H. captiosa is extended ventrally into a narrow fingerlike shape. The basistylus is straight for the basal three-fifths of its length and angled posteriorly at about two-fifths of its length from the apex (Fig. 2A). In H. serrata, the shape of the epandrium is variable, ranging from short and squared off (Fig. 2B) to extended ventrally (as shown in Dvořák and Dvořáková Reference Dvorak and Dvorakova2012, fig. 3), but the extension is generally shorter than in that of H. captiosa. A more reliable diagnostic character is the shape of the basistylus of H. serrata, which is broader, shorter, and curved along its length (Fig. 2B). Females were not examined as part of the present study, but according to Woźnica (Reference Woźnica2006), female H. captiosa have roughly circular spermathecae that are convex at the base, whereas those of H. serrata are concave at the base, giving them a mushroom-like shape.
Distribution. EUROPE: France, Germany, Poland, Hungary, Romania, Italy, Yugoslavia [sic], Bulgaria, Ukraine (Gorodkov Reference Gorodkov, Soós and Papp1984); Scotland (Papp Reference Papp1978); Austria, Wales (Papp Reference Papp1982); Czechia (Dvořák and Dvořákova Reference Dvorak and Dvorakova2012); Spain (Martín-Vega and Baz Reference Martín-Vega and Baz2013); Slovakia (Preisler et al. Reference Preisler, Roháček and Tkoč2022). NORTH AMERICA: Kentucky (the present paper).
Remarks. Gill (Reference Gill1962) recorded H. serrata as ranging from Canada and Alaska as far south as California, Tennessee, and Virginia, in the United States of America. The epandrium and basistylus (“epiphallic process”) illustrated by Gill (Reference Gill1962, fig. 89) are clearly that of typical H. serrata, but he did not indicate where the specimen depicted was collected. The identities of the specimens represented by Gill’s (Reference Gill1962, Reference Gill, Stone, Sabrosky, Wirth, Foote and Coulson1965) more southerly records are unclear, and re-examination of historical specimens is required to determine the Nearctic distribution of H. captiosa.
It is interesting to note that Garrett (Reference Garrett1925, p. 3) described Helomyza americana as the American form of Heleomyza serrata, in which “the inner clasp of the hypopygium [i.e., the basistylus] is shorter, more evenly curved and deeper. […] Two or three thousand roughly examined.” His description, although terse, appears to describe the genitalia of H. serrata and contrast them with those of H. captiosa, which Garrett treated as the typical European form of H. serrata. This suggests that, although H. captiosa is more widespread in the Palaearctic than H. serrata is (Gorodkov Reference Gorodkov, Soós and Papp1984), Garrett (Reference Garrett1925) considered H. serrata to be common in North America and did not consider H. captiosa to be typical of the Nearctic fauna.
An intermediate form is found in the United Kingdom, and in this form the epandrium is extended downward and the basal section of the basistylus is slightly curved or bent (Sivell et al. Reference Sivell, Stubbs and Andrews2025). It is possible that records of H. captiosa in Scotland and Wales published by Papp (Reference Papp1978, Reference Papp1982) are based on such specimens. The assignment of these specimens to one species or the other and their implication for the distinctness of H. serrata and H. captiosa require further study.
Taxonomy of Heleomyza Fallén
The genus Heleomyza Fallén, 1810 was previously delimited by Czerny (Reference Czerny1924) and Gill (Reference Gill1962) on the basis of the chaetotaxy of the head (two pairs of equal fronto-orbital bristles), prosternum (two or more pairs of bristles), and scutellum (lacking dorsal hairs). However, a study of the male genitalia led Gorodkov (Reference Gorodkov1962) to restrict Heleomyza (as Leria Robineau-Desvoidy, 1830) to only those species with the dististyli reduced and the basistyli comparatively much larger (Fig. 2). The remaining species, which display the plesiomorphic condition of well-developed dististyli, were transferred to Scoliocentra Loew, 1862 sensu stricto or to a new subgenus Scoliocentra (Leriola Gorodkov, 1962).
The genitalic and chaetotaxic characters given by Gorodkov (Reference Gorodkov1962) in revising the Palaearctic species are easily applied to the Nearctic species of Heleomyza sensu Gill (1962). Species of subgenus Leriola have a short basistylus that extends barely (or not at all) beyond the margin of the epandrium (Gorodkov Reference Gorodkov1962, figs. 19, 54; Gill Reference Gill1962, figs. 94, 95). In terms of external morphology, Scoliocentra (Leriola) species cluster into two groups. The Scoliocentra nigrinervis group can be distinguished from Heleomyza by the presence of darkened crossveins, and it includes two Nearctic species, S. (L.) maculipennis (Becker, 1897) (= Heleomyza difficilis Gill, 1962) and S. (L.) nebulosa (Coquillett, 1910) comb. nov. The Scoliocentra brachypterna group can be distinguished from Heleomyza by the presence of two strong pairs of vibrissae with short peristomal setulae at their base; the vibrissae were described as equal by Gorodkov (Reference Gorodkov1962), but in truth, the lower vibrissae are slightly shorter than the upper vibrissae (Woźnica Reference Woźnica2004). In Heleomyza species with two pairs of vibrissae, the pairs are more substantially unequal and (or) have enlarged peristomal setulae at their base (Gorodkov Reference Gorodkov1962). The Nearctic region contains one recognised species of this group, S. (L.) latens (Aldrich, 1896) comb. nov., which was formerly considered synonymous with the Palaearctic S. brachypterna (Loew, 1873) (e.g., Gill Reference Gill1962) but is now considered a distinct member of the S. brachypterna group (Gorodkov Reference Gorodkov, Soós and Papp1984; Woźnica Reference Woźnica2004). In specimens of S. latens examined by C.S.A., the lower vibrissae are about two-thirds the length of the upper vibrissae.
In addition, Gorodkov (Reference Gorodkov1962, Reference Gorodkov, Soós and Papp1984) removed Scoliocentra (Scoliocentra) dupliciseta (Strobl, 1894) from Heleomyza and transferred it to Scoliocentra sensu stricto, as this species has both the basistylus and dististylus well-developed. Like Heleomyza species, S. dupliciseta has hyaline wings and unequal pairs of vibrissae; however, it possesses a small but distinct proepimeral bristle that is absent in Heleomyza (Gorodkov Reference Gorodkov1962). The above chaetotactic and genitalic characters are shared by the Nearctic species Heleomyza bisetata (Garrett, 1922) (Gill Reference Gill1962, fig. 93), and the two species appear to be closely related. In addition, the species differs from Heleomyza by the presence of more than one strong bristle on the katepisternum, a character also shared by S. dupliciseta and S. latens. Accordingly, we transfer this species to Scoliocentra as S. (S.) bisetata (Garrett, 1922) comb. nov.
Finally, the genus Anypotacta Czerny, 1924, which possesses only a single pair of prosternal bristles, is now generally considered a subgenus of Heleomyza (e.g., Gorodkov Reference Gorodkov, Soós and Papp1984; Woźnica Reference Woźnica2006; Roháček et al. Reference Roháček, Tkoč and Preisler2017; but see Papp Reference Papp, Papp and Daras1998). Accordingly, we transfer the Nearctic species A. aldrichi (Garrett, 1921) and A. czernyi Gill, 1962 to Heleomyza and include them in the key below. However, the prior name Helomyza czernyi Collart, 1933 (in this case, we interpret “Helomyza” as an incorrect subsequent spelling of Heleomyza), makes Heleomyza czernyi (Gill, 1962) an invalid junior secondary homonym. In accordance with Article 60 of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999), we propose Heleomyza (Anypotacta) gilli nom. nov. (ZooBank Nomenclature Act: urn:lsid:zoobank.org:act:57ED5DDB-A4E8-4A78-B43F-64194C1D1783) as a new replacement name for Anypotacta czernyi, in recognition of the late Gordon D. Gill for his invaluable studies of Nearctic heleomyzid flies.
Key to Nearctic species of Heleomyza and similar species of Scoliocentra
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1. Katepisternum with one strong bristle, often with one or more additional short bristles anteriorly; crossveins of wings without infuscations; dististylus of male reduced, much shorter than basistylus (Fig. 2) …………………………………………. Heleomyza, 2
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–. Either katepisternum with two or more strong bristles or crossvein r-m infuscated; dististylus of male as well-developed as basistylus …………………………… Scoliocentra, 9
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2. Prosternum with two or more pairs of bristles ……………… subgenus Heleomyza, 3
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–. Prosternum with a single pair of bristles (females not identifiable beyond this point) ………………………………………………….… subgenus Anypotacta, 8
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3. Anepisternum bare (rarely with a small setula at the posterior margin); abdomen usually orange ………………………………………………………………. 4
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–. Anepisternum with bristles or setulae (if a single posterior bristle is present, it is strong); abdomen grey or brown ……………………………………………. 5
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4. Basistylus of male hockey stick–shaped, basally straight, and bent about two-fifths down its length from the apex (Fig. 2A); spermathecae of female round, convex at base …………………………………….. Heleomyza (Heleomyza) captiosa (Gorodkov, 1962)
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–. Basistylus of male banana-shaped, curved along its length (Fig. 2B); spermathecae of female mushroom-shaped, concave at base … Heleomyza (Heleomyza) serrata (Linnaeus, 1758)
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5. Anepisternum with 1–3 bristles in the middle of the posterior margin ……………. 6
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–. Anepisternum with setulae only, located in areas other than the middle of the posterior margin ………………………………………………………… 7
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6. Basistylus of male with spines covering the medial surface; all three spermathecae of female round……………………Heleomyza (Heleomyza) borealis (Boheman, 1865) (= tristissima Garrett, 1921; czernyi Collart, 1933)
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–. Basistylus of male with spines restricted to the posterior margin; spermathecae of female not uniform in shape: two spermathecae flattened apically, one round ……………………………………………… Heleomyza (Heleomyza) modesta (Meigen, 1835)
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7. Anepisternum covered extensively with setulae ……………………………………………………………. Heleomyza (Heleomyza) pleuralis (Becker, 1907)
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–. Setulae of anepisternum restricted to posteroventral corner ………………………………………………… Heleomyza (Heleomyza) genalis (Coquillett, 1910)
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8. Basistylus with two distinct lobes …………………………………………………………… Heleomyza (Anypotacta) aldrichi (Garrett, 1921) comb. nov.
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–. Basistylus single-lobed… Heleomyza (Anypotacta) gilli nom. nov. (= czernyi Gill, 1962)
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9. Crossveins hyaline; katepisternum with two or more strong bristles …………… 10
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–. At least crossvein r-m infuscated with brown; katepisternum with one strong bristle…11
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10. Thorax light brown; anepisternum with several bristles near the posterior margin; first hind tarsomere of male not shorter than second hind tarsomere …………………………………………… Scoliocentra (Scoliocentra) bisetata (Garrett, 1922) comb. nov.
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–. Thorax grey; anepisternum bare; first hind tarsomere of male shorter than second hind tarsomere…………………Scoliocentra (Leriola) latens (Aldrich, 1896) comb. nov.
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11. Posterior part of anepisternum and anterior part of anepimeron covered with setulae …………………….Scoliocentra (Leriola) maculipennis (Becker) (= difficilis Gill, 1962)
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–. Anepisternum and anepimeron bare…………………………………………………………….Scoliocentra (Leriola) nebulosa (Coquillett, 1910) comb. nov.
Acknowledgements
The authors thank Lisa Isaacs, for collecting the specimen of H. captiosa, and Bill Murphy, for his assistance in photographing the specimen. They also thank Giorgia Giordani, Stefano Vanin, and The European Zoological Journal for their permission to reproduce the photo of H. serrata in Figure 2B. Brendan O’Laughlin helped with the literature review, and Karina Zhuzenova helped with the Russian translation. Two anonymous reviewers provided helpful feedback on the manuscript.
Competing interests
The authors declare that they have no competing interests.
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