Athyreus soesilae Makhan, 2008

Hielkema, Auke J., 2017, Some corrections and remarks regarding the nomenclature of Neotropical Athyreini, Passalini, Phanaeini, Rutelini, Cyclocephalini, Dynastini and Oryctini (Coleoptera: Scarabaeoidea), Insecta Mundi 2017 (561), pp. 1-18 : 2-3

Synonymization of Athyreus soesilae Makhan, 2008 with Neoathyreus (Neoathyreus) excavatus ( Laporte, 1840) ( Geotrupidae : Bolboceratinae: Athyreini )

Makhan (2008: 1) describes the species Athyreus soesilae based on a type series of one male and four female specimens that was collected in Suriname. Judging by the rather short description, accompanying pictures and stated type locality, I suspected this species to be synonymous with a previously described species. Makhan (2008) states that the holotype of A. soesilae is deposited in the University of Suriname, Department of Entomology (= National Zoological Collection of Suriname, NZCS). However, upon my request to examine the holotype, Mr. Anielkoemar Gangadin, the long-serving Assistant Curator of Invertebrates of the NZCS, assured me they never received either the holotype or a paratype of this species. Regardless, I am confident that the following narrative amounts to a solid case for synonymization.

Howden and Martínez (1963: 348) split the genus Athyreus MacLeay, 1819 (p. 123) in four different genera, three of which occur in the Neotropics. Of these, the genus Parathyreus Howden and Martínez, 1963 (p. 348) has never been found north of the Amazon / Rio Madeira main stem ( Howden 1985b: 171). This leaves two relevant genera to consider here, namely Athyreus and Neoathyreus Howden and Martínez, 1963 (p. 350), both of which have several representatives in the Guianas. The characters mentioned in the generic key in Howden and Martínez (1963: 348) which are relevant with respect to Makhan’s brief description, are sexual dimorphism and size. The genus Athyreus is defined as having dissimilar sexes and a length of over 15 mm ( Howden and Martínez 1963: 348, 350; 1978: 2), while Neoathyreus has similar sexes and a length below 15 mm ( Howden and Martínez 1963: 348, 350; Howden 1985a: 3).

According to Makhan (2008), the sexes of A. soesilae are similar, with the male holotype having a length of 11 mm (no information is given regarding the four paratypes, except that they do not differ from the holotype and are all female). This clearly puts A. soesilae within the genus Neoathyreus , the existence of which was apparently unknown to Makhan. It is noteworthy that the only publication cited by Makhan is Howden and Martínez (1978), which does not cite the name Neoathyreus . However, in its introduction this publication does refer to Howden and Martínez (1963) and notes that the genus Athyreus is restricted “to include only a group of relatively large, sexually dimorphic species.” Evidently, Makhan did not notice this statement or chose to disregard it.

At present, seven species of Neoathyreus are known from the Guianas ( Boilly 2011: 24, 2014: 308), four of which have been found in Suriname (A. J. Hielkema, unpublished data). Makhan (2008) states his specimens were caught in “the north of Suriname,” later specifying “District Suriname.” In fact, the District Suriname was abrogated during the rearrangement of the Surinamese administrative regions, which took place several years before Makhan collected his specimens. The district was situated around the country’s capital Paramaribo and along both shores of the lower Suriname River. All of it was located in the coastal zone and the northern savanna belt ( Stichting Planbureau Suriname 1988: C1). Of the four known Surinamese species of Neoathyreus , two appear to be restricted to the forests of the interior, one ( N. (Neoathyreus) excavatus ( Laporte, 1840) (p. 103)) has as yet only been found in the coastal area and the northern savanna belt and one (likely N. (N.) lanuginosus ( Klug, 1845) (p. 28)) is found in the interior while a singleton of it was recently found in a flight interception trap in an old secondary forest in the coastal area (A. J. Hielkema, unpublished data).

Neoathyreus (N.) excavatus is relatively commonly collected at lights and in flight interception traps in the present districts Paramaribo and Para, which makes it the best candidate for Makhan’s specimens. In fact, N. (N.) excavatus was first reported for Suriname in Howden (1985a) and is at present still the only valid species published for Suriname. According to Makhan, at least one of his specimens was “collected on cow dung.” This substrate is not unusual for N. (N.) excavatus , as I once found a specimen of this widespread species in a tunnel under cow dung in Guatemala.

Makhan’s picture of the habitus of his type specimen is unfortunately too low-quality to clearly distinguish the species. However, when comparing his picture of the aedeagus of A. soesilae with the aedeagi of other Guianan Athyreini (see e.g. Boilly 2011: 30), a striking resemblance with that of N. excavatus can be seen, while it differs significantly from those of all the other possible species.

Based on the provided pictures and corroborated by the description and the type locality, and in accordance with ICZN (2012) Article 23.3, I therefore synonymize Athyreus soesilae Makhan, 2008 with Neoathyreus (Neoathyreus) excavatus ( Laporte, 1840) .

After his description of A. soesilae, Makhan (2008) comments that he believes that the Surinamese specimen of A. bellator Westwood, 1848 (p. 387) mentioned in Howden and Martínez (1978: 42) is probably a specimen of A. soesilae . Makhan acknowledges that he has not seen the specimen and remarks that the males of these two species differ externally as well as with regards to their genitalia. He does not mention the difference in size between his specimens (11 mm) and the size of A. bellator (17–22 mm) as mentioned in Howden and Martínez (1978). I am aware of three more specimens of A. bellator from Suriname, one of which I collected myself. Given Makhan’s clear lack of knowledge of the Athyreini , his disregard of the differences he mentions and the fact that Howden was at the time already a renowned specialist of world Geotrupidae , it may be concluded that Makhan’s remark is entirely unfounded.