Nothybus absens, Lonsdale, O. & Marshall, S. A., 2016

Lonsdale, O. & Marshall, S. A., 2016, Revision of the family Nothybidae (Diptera: Schizophora), Zootaxa 4098 (1), pp. 1-42 : 12-14

Nothybus absens spec. nov.

Figures 5–6

Description (female only, based on field photographs—Figs 5, 6)

Head: Base colour yellowish-brown with orange tint. Distal half of first flagellomere black, extending to distal 2/3 on inner surface. Face with ventral 2/3 silvery tomentose with small medial glossy black spot. Ocellar tubercle black. Frons with posterior velvety patch well-developed; anterior pair of patches fused on anterior half. Colour of clypeus and labellum unknown; palpus light yellow, at least apically.

Thorax: Base colour yellowish-brown with orange tint. Scutum with dark brown medial stripe bounded by four rows of acrostichal setulae, with margins ill-defined posteriorly. Scutellum and subscutellum dark brown. Dorsal margin of postpronotum brownish, with remainder of postpronotum covered by tomentose/iridescent stripe that continues to cover anterolateral margin of brownish notopleuron and most of anepisternum and katepisternum; remainder of anepisternum brownish; posterior region of notopleuron with second narrower, fainter tomentose stripe posteriorly joining broad anterior stripe on anepisternum. Laterotergites dark brown.

Wing: Wing length unknown. Vein r-m surrounded by broad dark spot. Transverse stripe dark, surrounding dmcu and filling apex of cell r1; stripe extending apically to surround clear iridescent spots, with only spot in cell r2+3 open to wing margin; brown clouds surrounding dm-cu and apex of CuA1. Centre of wing apparently without iridescence (possibly not visible due to angle of wing in photograph).

Legs: Legs light yellowish with apices of femora (for a length slightly longer than width of apex) and tibiae brownish-black. Tarsi dark brown; fore basitarsomere white with base brownish-black for a length approximately equal to width of segment. Mid and hind coxae light yellow (base not visible).

Abdomen: Tergites 1–3 dark brown with dorsum darker. Tergite 4 yellow with anterior margin, posterior margin and large posteromedial spot dark brown. Tergite 5 dark brown (texture not visible), possibly with posterlateral margin yellow. Remaining posterior segments yellow where visible.

Etymology. The specific epithet is Latin for “absent, missing, away, gone, physically elsewhere, nonexistent”.

Distribution. China (Guangxi).

Holotype. CHINA. Guangxi Province: near Nanning City, Damingshan National Reserve, Tianping Mountain, Ketao (??), 23°30′42.70ʺN, 108°26′35.76ʺE, 1241m, bamboo forest, near stream, 23.09.2012, Stephen A. Marshall (1♀, photo voucher only).

Comments. Fusion of the dark, velvety anterolateral patches on the frons is characteristic of this species and unique in the family. Also useful for diagnosis in combination are three clear, iridescent, linearly arranged subapical wing spots, a complete medial stripe on the scutum, a white fore basitarsomere with a narrowly black base, and a yellow tergite 4 with a brown anterior margin and posteromedial spot. There is some possibility that specimens of this or other Chinese Nothybidae are in the collection of the China Agricultural University (Beijing, China), but that collection has been under renovation for the several years we have been working on this revision and loans remain impossible (Ding Yang, personal communication 2015).

Discussion. The fly on which this description is based was photographed in the field, but not collected. According to article 73.1.4 of the International Code of Zoological Nomenclature (I.C.Z.N 1999), “designation of an illustration of a single specimen as a holotype is to be treated as designation of the specimen illustrated; the fact that the specimen no longer exists or cannot be traced does not of itself invalidate the designation”. Further, although article 16.4 of the International Code of Zoological Nomenclature requires all holotypes that are “extant” to be deposited in a collection, the holotype of N. absens escaped capture and cannot be considered “extant”. This description therefore meets the standards imposed by the International Code of Zoological Nomenclature, and is further justified by its context as a significant component of a comprehensive revision, and the fact that the photographs of the type include enough information for an adequate description and confident subsequent recognition of the species.

Marshall & Evenhuis (2015) recently discussed the legitimacy, and the pros and cons, of describing new species on the basis of character evidence captured in photographs of lost type specimens. While agreeing that preserved types are usually essential and always preferable as a basis for new species descriptions, they pointed out that there are circumstances under which new species could be confidently recognized and defined on the basis of photographs even if the type specimen is lost. Their paper, illustrated with a description of a distinctive new species of Bombyliidae , made a case for naming such species using the rules of nomenclature despite the absence of a type specimen. Unsurprisingly, given the centrality of the type concept in the science of taxonomy, the Marshall and Evenhuis paper ignited controversy, with both strongly supportive and vociferously negative comments. Given this set of circumstances it is necessary for us to discuss and further justify our decision to give Nothybus absens a name in the absence of a preserved type.

A revision such as this represents a compilation of all that is known about the taxonomy and distribution of the clade under study. It is routine to recognize towards the end of the long period required to complete such a revision that it is not possible to treat some component species in the same detail as others. A species might be represented only by a compression fossil, a badly damaged specimen, or a specimen of the “wrong” sex (for example, a female in taxa with important characters in the male genitalia). In such cases it is up to the judgement of the taxonomist whether to name the species or not but, in general, if there is no doubt that the species is distinct it will be given a name. Now that digital macrophotography has come of age and image collections are growing at a much faster rate than specimen collections, it is inevitable that some authors of taxonomic revisions will discover species represented only by photographs, perhaps because the authors themselves photographed but failed to collect a specimen or perhaps because the photographs were found in image collections made by others (just as we routinely find useful specimens in collections made by others). This situation is really no different from that routinely faced when only a damaged specimen or a singleton female is available, and the revising taxonomist should be free to use his or her judgement. If enough characters can be retrieved from the photograph to confidently recognize and define the species then science is best served by giving it a stable name. To put this argument in the context of the current revision, we are confident that the species described here as Nothybus absens is a distinct species, which gives us three choices about how to handle it: 1—ignore it until we get specimens, 2—name it informally as “ China undescribed Nothybus ” or something to that effect, 3—give it a unique name in the hope that it will be a stable and universal name for the species. Publishing without mention of the species would be dishonest, and waiting for specimens could indefinitely delay an otherwise complete and useful revision. Use of an informal name for a distinct species seems a bit of a throwback to pre-Linnean nomenclature when the ICZN is in place to help ensure that names are unique, universal and stable. We thus choose option 3, but feel compelled to defend this choice against some of the anticipated criticisms.

The most serious criticism leveled against describing species without an extant type is that such a description is “non-science”. This seems to suggest that describing this new species as “ China new species” would be acceptable, but naming it “ N. absens ” constitutes “non-science”. In fact, neither the nature of the name nor the presence or absence of a type has any bearing on whether a description constitutes “science”. Putative defining characters are testable by collection and examination of new material, with or without a type. A type can be studied in search of previously overlooked characters that might corroborate or refute the original hypothesis, but in practice this sort of work is normally done with non-type material. Preserved type specimens can help resolve the identity of a taxon when the original description and illustrations prove inadequate, but they are not the distinction between science and non-science.

A more commonly expressed criticism of a move towards describing species with lost types but with good photos is that it “sets a dangerous precedent” and that it opens the door to bad taxonomy. But this is faulty logic, as the door has always been open to bad taxonomy, albeit somewhat blocked by good reviewers and good editors. We think it will be much harder to slip poor work by reviewers, editors and the community when the basis for a description is an accessible image than when the basis is a dubious specimen deposited in a distant museum, especially a specimen deposited in one of many museums from which loans are difficult or impossible. But of course the ideal is to have both good images and good type specimens if possible.

There are drawbacks to a description without an accessible type. We would prefer to have a specimen to dissect, and to deposit for future study of further character sets. But, whether we call this species “new species x” or “ N. absens ”, our description of this species is a testable hypothesis that will stand or fall on the basis of future collections or observations. If the character states in our description turn out to apply to multiple species distinguishable only by male genitalia, then a neotype will be necessary and can be easily designated.

Figures

FIGURES 5, 6. Nothybus absens spec. nov., holotype female, China, © S. A. Marshall. Fig. 7: N. lineifer Enderlein, Sabah, male, © S. Gaimari. Figs 8 – 10: N. sumatranus Enderlein, Vietnam, male, © S. A. Marshall.