Abstract
A revision of the genus Eutaphroptinus is presented. Eutaphroptinus pseudonatalensis is proposed as a junior synonym of Eutaphroptinus natalensis. Illustrations showing some of the morphological variation are included, and new records of this now monotypic genus are also provided.
Introduction
A new genus of spider beetle from South Africa, Eutaphroptinus Borowski, was described in 2009 with two new species, E. natalensis and E. pseudonatalensis. While examining material in our possession, it became difficult to ascribe some of our specimens to either species, and they did not appear to be undescribed. Hence, we suspected that this genus included only one rather than two species, as first hypothesized. Examination of the two holotypes of Eutaphroptinus and further study of specimens support our hypothesis of a single species and that E. pseudonatalensis is in fact a junior synonym of E. natalensis. We take this opportunity to clarify the taxonomy, more thoroughly illustrate characteristic features and variation to assist in identification, and report several new records for this now monotypic genus.
Materials and Methods
Examination of the type specimens took place during a visit to the Natural History Museum, London (BMNH) by the second author in 2013; we also checked a borrowed paratype in our possession. Photographs were later used to confirm some of the morphological variation of the BMNH type specimens and for comparison with material in our possession. Specimens from the following collections were also examined. Ditsong National Museum of Natural History, Pretoria (TMSA), National Collection of Insects, Pretoria (SANC), and the collection of the second author, Western Kentucky University, Bowling Green (TKPC).
Label data for type specimens are included and new records recorded verbatim. Label data for all other materials are recorded as follows: Country; geographic locality; additional collecting data; coordinates; altitude; date; collector; specimen code.
QGIS 3 was used to create a distribution map with ESRI Satellite and ESRI Boundaries & Places base map layers imported using the Quick Map Services plugin.
Taxonomy
Eutaphroptinus natalensis Borowski, 2009
Eutaphroptinus pseudonatalensis Borowski, 2009 syn. n.
Discussion
Some species of spider beetles appear to be highly variable in many morphological features, making it difficult at times to hypothesize species limits. This variability can include both external characteristics as well as the internal feature of male genitalia shape (e.g. Philips & Smith 2016, Philips & Dickmann 2018). Hence, some proposed species will later be hypothesized as synonyms, and some synonyms will be resurrected as valid species. This is a valuable process in the science of taxonomy and is not necessarily a negative criticism on the abilities and expertise of the original describer or synonymizer; taxonomy can be a challenging endeavor. Further collections and study of specimens, including the gathering of molecular evidence and clarification as to what evidence one should use to define species, will continue these taxonomic refinements.
Eutaphroptinus natalensis and E. pseudonatalensis were described from 14 and three specimens, respectively (Borowski 2009). Differentiation of the two species was based on several characteristics, including some that can be highly variable within species of spider beetles. Based on the study of types and our new material, features involving color and the shape of the elytral setae that were primarily used to differentiate the two species were found not useful for species delimitation. For example, antennomere color is described in E. natalensis as “first two black, others bicolorous: basal halves red, apical black”, while the antennomeres of E. pseudonatalensis are “first two black, others reddish-brown.” However, among the specimens of Eutaphroptinus examined, the amount of red and black in the antennomeres is variable and not consistent with other potential species-level differentiating characters. Excluding the basal antennomeres, which are typically dark-colored, the remaining antennomeres are usually bicolorous (apically black and basally red or reddish-brown) or can be nearly entirely red or reddish-brown. Additionally, the holotype of E. pseudonatalensis does have some black coloration in the more distal antennomere apices, similar to that found in specimens one would designate as E. natalensis.
Leg coloration for E. pseudonatalensis was described as yellowish-red, while E. natalensis was described as possessing reddish-brown tarsi and tibia, with the “femora darkened apically or blackish brown.” However, additional specimens examined reveal a continuum of leg coloration from yellowish-red to dark reddish-brown.
There are up to four types of elytral setae in many species of spider beetles. The most minute type is found within the punctures; the second and third longer types are located both between and along the puncture rows. The fourth is composed of fine recumbent setae or scales that are distributed in patterns that are species-specific. Eutaphroptinus possesses all four setal types, and two of these were used to differentiate species.
Elytral scales in E. natalensis were described only as “narrowly elliptical”, while the elytral scales of E. pseudonatalensis were “short, wide, silvery-white or greyish-blue.” Indeed, the holotypes do possess different scale color and morphology: dorsally E. natalensis has more elliptical “yellowish” (or pale tan-colored) scales while E. pseudonatalensis has teardrop-shaped whitish-colored scales. However, examination of other specimens of Eutaphroptinus reveals that some individuals possess both scale shapes or have intermediates of those shapes. Moreover, both scale morphologies can be either “yellowish”, white, or tan-colored, even within the same specimen (see Figs 1, 3, 7, and 10 for examples of scales of different colors and shapes).
Habitus of four different specimens of Eutaphroptinus natalensis. – 1, dorsal habitus, Mbotje Forest, Eastern Cape; 2, dorsal habitus, Lajuma Nature Reserve, Limpopo Province; 3, dorsal habitus, Kosi Bay, Manguzi Forest, Kwazulu-Natal; 4, lateral habitus, De Hoop, Western Cape.
Citation: Tijdschrift voor Entomologie 162, 1 (2019) ; 10.1163/22119434-20192083
Eutaphroptinus natalensis. – 5, ventral; 6, frontal; 7, close-up of elytral punctures. The obliquely oriented setae in this specimen are visible along the first five puncture rows.
Citation: Tijdschrift voor Entomologie 162, 1 (2019) ; 10.1163/22119434-20192083
Eutaphroptinus natalensis. – 8, dorsal habitus; 9, dorsal pronotum; 10, lateral pronotum and head. Note the distinct transverse groove at the base of the pronotum.
Citation: Tijdschrift voor Entomologie 162, 1 (2019) ; 10.1163/22119434-20192083
The pattern on the elytra formed by the scales was also used to differentiate the species (Figs 1–3). Eutaphroptinus natalensis was described as possessing “two transverse bands” of elytral scales in the anterior and posterior portions of the elytra, while E. pseudonatalensis has scales “dispersed all-over elytral surface sometimes with tendency to gather into transverse bands.” Although less distinct, the scale pattern on the E. pseudonatalensis holotype tends towards transverse bands in the same location as the bands in E. natalensis. The only noticeable difference seen between the holotypes is that E. pseudonatalensis has less dense and more scattered scales present between the two bands. Other specimens examined possess varying numbers of scales, but all tend towards the two-transverse-bands pattern and usually with additional scales located between the bands. Further, the transverse band near the elytral apex typically consists of two patches with occasionally a smaller one between these on each elytron. One should note that scale patterns in spider beetles can be quite variable within a species (e.g. see Philips 1998 for variability in Niptinus niveus Gorham, 1883) and can even sometimes be due simply to the loss of scales from abrasion; in some cases this loss can cause difficulty in species differentiation and identification.
Orientation of the setae along the puncture rows was reported as slightly different in each species. In E. natalensis, “on first 4 intervals, hairs point in part obliquely towards sides and apex.” In E. pseudonatalensis, they were described as “directed somewhat obliquely lateroposterial on first two intervals, towards elytral apex otherwise.” The elytral setal orientation is slightly variable among specimens studied, and further the obliquely oriented setae are found on the first two but may occur on as many as the first five intervals on each elytron depending upon the specimen examined (see Fig. 7 for setae obliquely oriented on first five intervals). Finally, in Fig. 2 of Borowski (2009), the elytral punctures are illustrated in an anterior-right to posterior-left direction. However, the punctures are actually oriented on the opposite diagonal (cf. Fig. 7).
Although the genitalia, as illustrated, show slight differences between the two species, this variation is similar to what has been documented elsewhere within various species (e.g., see Bellés 1985, Philips & Smith 2016, Philips & Dickmann 2018). Therefore, these slight morphological differences are hypothesized as only intraspecific variation.
Overall, none of the characters used to differentiate the two species (leg and antennal coloration, elytral scales and setae, etc.) correlate with each other in specimens examined. Instead, specimens possessed characteristics of both species or characteristics intermediate of the two species described. Hence the best hypothesis for species limits is a single species within the genus Eutaphroptinus.
Notes on the genus
The median lobe of the male genitalia in this genus is about as long as the parameres, a characteristic unique within the spider beetles. (NOTE: In the vertical orientation of Figs 4 and 7 in Borowski (2009), the median lobe appears smaller than the parameres.) This genus also possesses a characteristic deep and transverse pronotal groove near the base of the pronotum (see Figs 8–10). A pronotal groove can be found in other spider beetle taxa, including the genera Eutaphrimorphus Pic, 1898 and Silisoptinus Pic, 1917 as discussed by Borowski (2009), as well as Dignomus Wollaston, 1862 and Trymolophus Bellés, 1990. Eutaphroptinus can be distinguished from the South African genus Eutaphrimorphus by the structure of the pronotum and the groove. Eutaphroptinus possesses three dorsally projecting knobs on the disc of the pronotum (one larger one medially and two slightly smaller ones laterally; Fig. 6), compared to four shorter knobs in Eutaphrimorphus (all on either side of the midline). Additionally, the medial portion of the pronotal groove is much larger in Eutaphrimorphus than in Eutaphroptinus. Dignomus, a genus found in Africa, southern Europe, and the Middle East, possesses only two projections on the pronotum which are often more setose than in Eutaphroptinus. Dignomus also possesses lateral cavities on the pronotum, which are lacking in Eutaphroptinus. The pronotal morphology may indicate a close relationship with sympatric genera, most likely Dignomus and/or Eutaphrimorphus, but is not clear at this time.
Silisoptinus, known from Zanzibar (Tanzania) and Socotra Island (Yemen), also has a much larger medial depression in the transverse pronotal groove than Eutaphroptinus. Silisoptinus can be further differentiated from Eutaphroptinus by a very characteristic anteriorly widened prosternum present in the latter genus (for a more complete discussion see Borowski 2009). Trymolophus can be differentiated from Eutaphroptinus by a lack of a medial depression in the transverse groove. A transverse pronotal groove can also be found in Ptinus espanyoli Bellés, 1997, Ptinus augustithorax Bellés, 1986, and in the genus Tropicoptinus Bellés (1998). However, these taxa are all Neotropical and are also easily distinguishable from Eutaphroptinus by other features.
Distribution
Eutaphroptinus is now known to be distributed in South Africa along the coast from the southwestern Western Cape to Limpopo Province in the north (Fig 11). Additionally, there was one specimen collected in Tanzania. The population therefore extends through Mozambique, and the absence of records in that area is no doubt due to lack of sampling. This distribution is not unusual and is similar to other species of beetles such as the buprestid Sternocera orissa Buquet, 1837 (Holm and Gussmann 1992) as well as the more closely related spider beetle Ptinus peringueyi Pic, 1896, a taxon found in northern South Africa through Botswana to at least as far north as Tanzania (Philips & Smith 2016).
Distribution map of Eutaphroptinus. Red diamonds represent type localities for E. natalensis, the yellow circle is the type locality for E. pseudonatalensis, and blue triangles are new records for E. natalensis.
Citation: Tijdschrift voor Entomologie 162, 1 (2019) ; 10.1163/22119434-20192083
Type material
Eutaphroptinus natalensis. Holotype and paratype, males: South Africa, “Natal: Kloof. 1500 ft. Aug. 1926, S. Africa, R. E. Turner, Brit. Mus. 1926-350” (BMNH).
Eutaphroptinus pseudonatalensis. Holotype, male: South Africa, “Port St. John, Pondoland, July 10-31.1923, S. Africa, R.E. Turner, Brit. Museum. 1923-398” (BMNH).
Additional material examined/new records. South Africa, Eastern Cape, Mbotjie forest, forest litter & bark, 31.27 S, 29.43 E, 30.xi.2003, leg. M. Burger, R. Müller, E-Y:3580, 1 ♂ (TMSA); Limpopo Province, Lajuma National Reserve, sifting, canopy forest, 23.02 S, 29.26 E, 12.xii.2017, leg. Ruth Müller, E-Y:4012, 2 ♂ (TMSA); KwaZulu-Natal, Kosi Bay, Manguzi Forest, sifting, 26.59 S, 32.44 E, 15.xi.2002, leg. Burger, Harrison, Müller, E-Y:3537, 1 ♀ (TMSA); KwaZulu-Natal, Kosi Bay, Manguzi Forest, general collecting, 26.59 S, 32.44 E, 15.xi.2002, leg. Burger, Harrison, Müller, E-Y:3538, 1 ♀ (TMSA); Cape Province, The Claims’ Farm, nr. Komga Kubusi R. Valley, 32.29 S, 27.53 E, 01.xii. 1992, leg. R. Oberprieler, 1 ♂ (SANC); Western Cape, De Hoop, 34°27’15’ S, 20°23’49” E, 17 m, 10.i.2008, leg. T. K. Philips, 1 ♂, 1 ♀ (TKPC).
Acknowledgements
We are very grateful to the following curators for providing us with the opportunity to study specimens in their care: Ruth Müller and the late Charles Bellamy (Ditsong National Museum of Natural History, Pretoria), and Riaan Stals and Beth Grobbelaar (National Collection of Insects, Pretoria). The authors also appreciate the support of the Center for Biodiversity Studies at Western Kentucky University and an NSF Biological Surveys and Inventories grant (DEB 0430132). Finally, we would like to thank the anonymous reviewers for their suggestions for improving this article.
References
Bellés X. , 1985. Sistemática, filogenia y biogeografía de la subfamilia Gibbiinae (Coleoptera: Ptinidae). – Treballs del Museu de Zoologia 3: 1–94.
Borowski J , 2009. The spider beetles of the continental Africa (Coleoptera: Ptinidae). Part III. Eutaphroptinus gen. n. from South Africa with description of two new species belonging to the new genus. – Studies and Reports of District Prague-East, Taxonomical Series 5: 11–16.
Holm E. & Gussmann S. , 1992. Revision of the genus Sternocera Eschscholtz of Africa (Coleoptera: Buprestidae). Entomology Memoir No. 85. – Agricultural Research Council, Pretoria, South Africa, 86 pp.
Philips T. K. 1998. A new genus and species of putatively myrmecophilous ptinine: Coleoaethes tetralobus (Coleoptera: Anobiidae: Ptininae). – Pan-Pacific Entomologist 74: 113–117.
Philips T. K. & Dickmann R. L. , 2018. A new species of Mezium Curtis (Coleoptera: Ptinidae) from South Africa, with notes on the genus and species limits. – The Coleopterists Bulletin 72: 317–330.
Philips T. K. & Smith A. L. , 2016. New records for Ptinus peringueyi Pic (Coleoptera: Ptinidae) and a discussion of morphological variation in this species. – The Coleopterists Bulletin 70: 403–406.
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