Results are presented of a study on the armature of the hind and fore tibiae in 39 species and 4 additional subspecies, out of 54 (formally recognised) species and 9 additional subspecies, belonging to Rhacocleis and Pterolepis. The armature of the hind tibia, traditionally used to separate Pterolepis and Rhacocleis, varies within taxa from very slight in most taxa to extensive in a few. The armature of the upper inner margin of the fore tibia proved a more reliable character than the traditional hind tibial armature to separate Pterolepis and Rhacocleis, indicating that the synonymy of Rhacocleis with Pterolepis proposed in Heller et al. (1998), should be re-evaluated. Observations suggest a possible re-arrangement of species described under Pterolepis and Rhacocleis, but no nomenclatural changes are proposed. It is argued that nomenclatural changes, if any, should only be taken after a much needed review of the generic definitions in the Platycleidini (s.l.). An updated checklist of Pterolepis and Rhacocleis taxa is included. Pterolepis ramburi Serville 1838 is proposed as a species incertae sedis.
Introduction
From the beginning the name Pterolepis has been misinterpreted, causing much nomenclatorial confusion. Rambur described Pterolepis spoliata gen. and sp.n. in his survey of the entomological fauna of Andalusia, southern Spain. Rambur's publication on the Orthoptera was issued partly in 1838 (pp. 1–16) and partly in 1839 (pp 17–94), the latter including the description of Pterolepis (p. 59). In that description it is clearly stated that the prosternum bears 2 spines: “prothorax ayant, en dessous, deux petites pointes et une autre en dessus à ses hanches”. In a footnote, Rambur mentions having before him a second member of his genus, “Corsica” in litt., that he then had delivered to Serville for further description (no doubt because its locality Corsica was outside the scope of his Andalusian fauna).
Serville's (more correctly Audinet-Serville's) work on Orthoptera was published in 1839 (some claim 1838), the same year as Rambur's paper. Serville incorrectly described and arranged the genus Pterolepis (the author's name correctly assigned to ‘Rambur in Andalusian Fauna’) under the genera with an unarmed prosternum, representing members of Pholidopterini (and possibly one member of Antaxius Brunner 1882). At the same time, Serville erected the genus Thyreonotus for Rambur's species corsicus (in litt.) because of its spined prosternum (and thus correctly distinct from his (Serville's) Pterolepis (=Pholidoptera Wesmael 1838, partim). Rambur's species spoliata is not mentioned in Serville's work. Apparently the text of Rambur's paper had not reached Serville in time to incorporate it in his major contribution.
Thus, from the very beginning (1839), there were 2 versions of the name Pterolepis, the original one of Rambur—with spined prosternum—and the misinterpretation in Serville—with unarmed prosternum.
Fieber (1853/1854), in his ‘Synopsis’, followed Serville's interpretation of Pterolepis and erected Rhacocleis for 2 new species with a spined prosternum: annulatus and discrepans (= germanica Herrich-Schaeffer). Fieber grouped his new genus with Thyreonotus. Though he didn't indicate the distinction he drew between Rhacocleis and Thyreonotus, it was most likely based upon their different mesoand metasterna and male cerci. The meso- and metasternum are acutely pointed in Thyreonotus (in agreement with Serville's description: “Présternum fortement bidenté, ainsi que le mésosternum et le métasternum [in italics]”) against simple triangular lobes (Fieber's Rhacocleis: “Mittel- und Hinterbrustlappen dreieckig”). The male cercus in Thyreonotus is wide and flattened medially, without basal tooth, but in Rhacocleis, quoting Fieber: “Raife des Mannes pfriemlich, am Grunde ein Dorn”. Either Rambur's original description of Pterolepis was not available to Fieber or misinterpreted by him, because he arranged Rambur's spoliata under Serville's Pterolepis species with unarmed prosternum.
Fieber's study was issued in the same year as Fischer's ‘Orthoptera Europaea’(1853). Fischer, however, recognized Serville's confusion, erecting his genus Thamnotrizon (=Pholidoptera) for Serville's Pterolepis, and arranged under Pterolepis Rambur's spoliata, as well as Herrich-Schaeffer's germanica (1840, as Decticus), his modesta (=germanica) but also pedestris (Fabricius 1787) and his spinibrachius (both now Antaxius). So it happened again that 2 important papers were published almost simultaneously, resulting in confusion mainly by Fieber's misinterpretation of Serville's Pterolepis.
Herman (1874) again stressed the importance of the distinction between unarmed and bispinose prosterna and grouped Rhacocleis, Thyreonotus, Pterolepis and other genera with armed prosternum versus Decticus Burmeister 1838, Thamnotrizon (=Pholidoptera) and other genera with unarmed prosternum. However, Herman distinguished Pterolepis from Rhacocleis using the length of the plantulae, as did Fischer for a subgroup of Pterolepis (sensu Fischer). As a result, Herman's Pterolepis refers to what is now arranged under Antaxius.
Within the group of genera with a bispinose prosternum, Brunner von Wattenwyl (1882) distinguished Pterolepis from Rhacocleis on the number of spurs at the tip of the hind tibiae, grouping among other genera, Drymadusa Stein 1860, Gampsocleis Fieber 1852 and Pterolepis with 4 spurs, against Rhacocleis, Thyreonotus. and Antaxius with 2 spurs. A further subdivision of both groups was based on the length of the plantulae: short in Drymadusa, long in Gampsocleis/Pterolepis and short in Thyreonotus and Antaxius and long in Rhacocleis. This arrangement, with a number of additions and modifications, has been followed since in Brunner (1893), Kirby (1906), Caudell (1908), Harz (1969) and up to the present time.
Besides the obvious nomenclatorial confusion, a close examination of references dealing with the systematics of Pterolepis versus Rhacocleis, shows that the number of ventral spurs at the tip of the hind tibia has always been the traditional key character to distinguish Pterolepis from Rhacocleis. Uvarov (1942: 315–316), while describing R. graeca Uvarov 1942, noticed that the hind tibiae in all males had outer spurs but no inner spurs; whereas in the female type specimen, one hind tibia showed an under-developed inner spur, the other one lacking such a spur. He remarks that his new species might be referred to Pterolepis Rambur 1839, which differs from Rhacocleis in this particular character, i.e., presenting not only outer spurs but also inner spurs (although shorter than the large outer spurs). Quoting his words: “The importance of this character appears somewhat uncertain, although it is used to separate not only genera of Decticinae, but even larger groups”.
Likewise in some North African species assigned to Rhacocleis (silviarum Galvagni 1984; moralesi and adolphorum, both Galvagni 1988; pieltaini Morales Agacino 1940 and (?) maroccana Bolívar 1905), the tip of the hind tibia presents individually a single or 2 inner spurs, commonly unilateral and much reduced in size, or only a pair of sockets or pits without any spur. These aberrant armatures have been described, figured and discussed in Galvagni (1984: 90, fig. 8–9; 1988: 43, 62, 67, fig. 16), who assumes that these are anomalous exceptions that probably do not undermine the reliability of the key character between Pterolepis and Rhacocleis.
Heller (1988) remarks that the habitus of Rhacocleis, particularly of graeca, closely resembles that of Pterolepis. He noticed that the armature of the tip of the hind tibia is variable, both in Rhacocleis and Pterolepis, pointing out that this character is not always reliable as a generic key character. Heller (1988) then emphasised that if no other distinctive character between Pterolepis and Rhacocleis can be found, it is necessary to synonymise these genera. When compiling a checklist of European Orthoptera, Heller et al. (1998) stressed again the lack of distinct features between the genera and consequently listed all European species formerly arranged under Rhacocleis under Pterolepis (its senior synonym).
In the process of dealing with the generic assignment for 2 recently discovered tettigonid species (Willemse & Willemse, this issue), the distinction between Pterolepis and Rhacocleis has been re-evaluated. Particulars of the armature of the legs of more than 1000 specimens, representing 43 taxa (out of about 63 presently recognized formal taxa, including subspecies) were studied by the present authors and the following orthopterists: B. Çiplak, P. Fontana, A. Galvagni, K.-G. Heller, R. Kleukers and J. Tilmans (Tables 1, 2).
Armature of the hind tibiae
Two pairs of spurs occur on the lower (ventral) side of the tip of the hind tibia: 1) a pair of long spurs located, one on the outer, one on the inner side, and commonly named the ‘outer apical spurs’ (Fig. 1, A, B) and 2) an additional pair of much shorter ones, located in between the others, commonly named the inner apical spurs (Fig. 1, c, d). Within Pterolepis/Rhacocleis is found a full range—from well-developed inner spurs (though never as strong as the outer spurs) to rudimentary sockets with a hair or without any projecting structure, to the complete absence of even such rudimentary sockets (Fig. 1: 1–8).
Well-developed inner spurs at the tip of the hind tibia are considered typical for Pterolepis, while absence of these spurs is considered typical for Rhacocleis (though sockets may be present, even one bearing a hair, but with any true spur absent). Indeed, this situation fits the few available specimens of the type species of both genera, Rhacocleis annulata Fieber 1853 and Pterolepis spoliata Rambur 1838. However, in a few individuals of some subspecific taxa of the latter, the inner spurs are reduced in size and even lacking. Likewise some variation is found among members of Rhacocleis. The observation that a complete absence of inner spurs in Rhacocleis is not always true, as noted in Uvarov (1942), Galvagni (1984, 1988) and Heller (1988), could be confirmed. Within Pterolepis and Rhacocleis the number of apical spurs of the hind tibia varies, not only between conspecific specimens, but even unilaterally within a single specimen. While in Pterolepis it's quite exceptional that the inner spurs are reduced or lacking, in Rhacocleis the variation is more remarkable. In some populations of R. germanica 1 or 2 inner spurs are present in almost half the studied specimens. The results of our observations are given in Table 1, column E.
Armature of the fore tibiae
The armature of the upper outer (“posterior”) margin of the fore tibia (Fig. 2), especially presence or absence of an outer apical spur, has been used extensively in traditional classification, even to discriminate between subfamilies and tribes. This margin commonly shows a spur at the distal end of the tympanal opening, 1, 2, or exceptionally 3, on the mid part, and one apical spur on the tip. This armature is found in both Pterolepis and Rhacocleis, as well as in most other examined genera of the Platycleidini (s.l.) [not defined in Harz (1969) or c.f. Otte et al. (2004), but in Zeuner (1941), and redefined in a much broader sense in Rentz & Colless (1990) and followed in Otte ex aff. (2004)].
The armature of the upper inner (“anterior”) margin of the fore tibia received less attention in this group of species. Exceptions, where the armature of the inner margin of the fore tibiae is mentioned, are Bolívar (1899), differentiating his Scirtobaenus lusitanicus (now Rhacocleis) from Pantel's grallatus (now Pterolepis spoliata grallata), a remark in Uvarov (1942), one of the 82 characters used for a numerical analysis in Rentz & Colles (1990) and comments in Çiplak (2000). Uvarov (1942) remarks that in R. silvestrii (cited as uvarovi, see also Ramme (1951) and Willemse (1982)) the armature of the front tibia bears spines on its upper side, 3 external, and 1 internal, “while in all other species of the genus the numbers are four and two, respectively. It is probable that these differences are of generic value, but it appears wiser to refrain from erecting a new genus until the numerous species of Rhacocleis are better known”.
Results of the present study are given in Table 2 (column E) and indicate that Pterolepis and Rhacocleis not only differ in the armature of the fore tibia, but also that this character is less variable than the armature at the apex of the hind tibia. The studied material shows that in all taxa assigned to Pterolepis, the upper inner margin of the fore tibia invariably is unarmed, as in most Platycleidini (s.l.).
In Rhacocleis, however, the situation is more complicated. The upper inner margin in most species, including the type species, presents 1 to 3 spurs, a basal one at the distal end of the tympanal opening, one halfway on the length and sometimes a third distal spur (Fig. 2). In Rhacocleis species from northwestern Africa, as far as examined, this margin is unarmed as in Pterolepis (with exception of one specimen of augustini Galvagni 2001 that unilaterally bears a single spur). A bilaterally unarmed upper inner margin is found also in about half the specimens of R. poneli Harz & Voisin 1987 from southeastern France and in 1 to 2% of neglecta (Costa 1863) from Italy. In all other species assigned to Rhacocleis, as far as studied, this margin may also be unarmed, but if so then not bilaterally, only unilaterally. This situation was seen in R. grisea Baccetti 1991 from Sardinia, insularis Ramme 1928 from the Aegean islands and derrai Harz 1983 from Crete.
Discussion
The general range of Pterolepis and Rhacocleis surrounds the Mediterranean, reaching roughly from the Iberian peninsula and opposing northwest Africa, eastward along Mediterranean northern Africa, via Israel to Anatolia, then back west to the Balkans, (extending north and east) and to Italy and south France, and including many Mediterranean islands. Though our observations of numbers of specimens and taxa are only extensive, not exhaustive, they suggest a correlation between the armature of the upper inner margin of the fore tibia and this geographical distribution (Table 2). One can recognise 2 groups: 1) taxa with this margin unarmed and 2) those presenting at least one spur unilaterally (average 0.5 spurs per tibia).
The geographical range of Group 1 covers the southern Iberian Peninsula, the islands of Sardinia and Sicily, and extends from northwestern Africa to Libya, including Egypt (?) (R. bidens Uvarov). That of Group 2 reaches from Israel (?) (R. ayali Karabag), through Anatolia, via the Aegean islands and the Balkans to Italy, including Sicily, Sardinia and Corsica, reaching southeastern France and the Iberian species R. lusitanica.
The first group contains all species described under Pterolepis, including its type species P. spoliata, the Iberian grallata Pantel 1886 (described under Scirtobaenus), the species from Sardinia and Sicily described under Pterolepis, probably the northwestern African species Pterolepis theryana Uvarov 1927 (not studied), but also, as far as studied, all African species assigned to Rhacocleis (a large number, see Table 1, 2, columns A, B).
The second group fits the type species of Rhacocleis, R. annulata and all taxa, as far as studied, described under Rhacocleis and ranging from Israel (?) (R. ayali not studied), through Anatolia, the Aegean and the Balkans, Italy, the islands of Sardinia, Sicily and Corsica, reaching southern France and part of Iberia.
Apparently members of both groups occur in Sardinia and Sicily: :Rhacocleis grisea and R. minerva, both Baccetti 1991, with Pterolepis pedata (Costa 1882); Rhacocleis annulata Fieber 1853 with Pterolepis elymica Galvagni & Massa 1980 (R. berberica dubronyi Baccetti ex aff.. 1995 not studied).
The position of R. poneli is interesting. The upper inner margin of the fore tibia is either bilaterally or unilaterally armed with a single spur; but in about half the studied specimens it is bilaterally unarmed; among our studied material this is an exceptionally poorly developed armature. In combination with this species' occurrence in southern France, this is noteworthy because it bridges the unarmed condition in Iberian species assigned to Pterolepis, with the armed one in Italian and eastern European species arranged under Rhacocleis.
Conclusion
Without doubt Pterolepis and Rhacocleis are closely related species groups. The armature of the apex of the hind tibia in Pterolepis and Rhacocleis varies within taxa from not armed or very slightly so in most, to considerably armed as in, e.g., R. germanica. The armature of the upper inner margin of the fore tibia appears to be a more stable character than that of the tip of the hind tibia.
The present observations are suggestive of a re-arrangement of the species described under Pterolepis and Rhacocleis, either as species groups, subgenera or genera (Table 2, column F). However, in the interest of stability of nomenclature, we propose for the time being, to continue the current classification as given in Otte (1997), Naskrecki & Otte (1999) and Otte ex aff. (2004) (Table 1, 2, column A).
A re-evaluation of the status of taxa arranged under Pterolepis/ Rhacocleis should not only be based on more material, but include as well nonmorphological characters. And ideally, it should be carried out in conjunction with a wider and much needed critical review of the generic definitions in the Platycleidini (s.l.). It is emphasised that the presence of one or more spurs at the upper inner margin of the fore tibia, as observed in a number of species presently arranged under Rhacocleis, is quite exceptional among Platycleidini (s.l.), particularly among palaearctic members of this tribe. Further analysis would be most welcome.
Checklist of taxa recognized in Pterolepis Rambur 1838 and Rhacocleis Fieber 1853
An updated checklist of taxa presently recognized in Pterolepis and Rhacocleis is presented in column A of Table 1 and 2, together with their approximate distribution (B) and the armature of the ventral side of the apex of the hind tibia (column E of Table 1) and of the upper inner margin of the fore tibia (column E of Table 2), as far as examined in this study. This checklist deviates considerably from those in Otte (1997) and Naskrecki & Otte (1999), but is only slightly at odds with a recent version of the Orthoptera Species File Online (Otte D. et al., version 15 January 2005).
Alterations to the latter are as follows: Rhacocleis silviarum Galvagni 1984, R. lagrecai Fontana & Massa 2004, R. andikithyriensis Tilmans [in press] and Pterolepis spoliata raggei Galvagni 1981 [not synonymised in Heller (1988)] are added; R. neglecta corsicana Bonfils 1960 is given species status in Galvagni (1976); some corrections refer to Pterolepis spoliata llorenteae [Galvagni (1981), nec llorente], Rhacocleis annulata [nec annulatus, gender of Rhacocleis feminine], R. silvestrii [Ramme (1939;1951), nec sylvestrii], R. tyrrhenica [La Greca (1952), nec thyrrhenica] and R. werneri Willemse [Willemse (1982), nec Hong].
Rhacocleis ramburi (Serville 1838) was described under Pterolepis together with 3 other species: the first representing Eupholidoptera chabrieri (Charpentier 1825), the second ramburi, sp.n., described after a female from southern France, the third Pholidoptera griseoaptera (DeGeer 1773) and the last as armillata sp.n., probably representing an Antaxius species.
The identity of Pterolepis ramburi has always been obscure. Brunner v. Wattenwyl assigned it doubtfully under Pholidoptera aptera (Fabricius) (Brunner 1861: 297, as Thamnotrizon) and later under Rhacocleis neglecta (Costa) (Brunner 1882: 323, as Rhacocleis bormansi sp.n.). Also Bolívar (1899: 153) arranged Serville's species doubtfully under Antaxius pedestris (Fabricius), including Seoane's (1877) record of Thamnotrizon ramburi Serville from the Pyrenees. Finot in his Faune de la France (1890) even omitted Serville's taxon. Both Kirby, in his Synonymic Catalogue II (1906: 187) and Caudell, in his decticine part of the Genera Insectorum (1908: 5) listed Pterolepis ramburi Serville under Rhacocleis without further comments. Since these publications, records of this taxon have not been found, including Chopard (1951) and Harz (1969). Though from the description and context, Pterolepis ramburi might represent Pholidoptera femorata (Fieber 1853) (or Pholidoptera aptera (Fabricius 1793) or Rhacocleis poneli, cf. coloration hind femur, but improbable because of spined prosternum), its identity will stay uncertain as the type is lost. Because the name of P. ramburi seems to have never been used again in almost a century, and because the type is unknown and its identity obscure, we propose Pterolepis ramburi Serville 1838 as a species incertae sedis: we omitted it from our checklist.
In Otte et al. (2004) citation on the synonymy of Scirtobaenus is incomplete. Uvarov (1930) described Scirtobaenus turcicus but, agreeing with Ramme's opinion, Uvarov transferred his species to Rhacocleis some years later (1934: 58), pointing out as “SYN.NOV.” that Scirtobaenus is just a junior synonym of Rhacocleis. In Harz (1969) Scirtobaenus is included in Rhacocleis (both grallata and Bolivar's lusitanicus) but the citation of this synonymy is lacking. The type species of Scirtobaenus is grallata Pantel 1886 (originally monotypic). Heller (1988) transferred grallata, arranged under Rhacocleis in Harz (1969), to Pterolepis as a subspecies of P. spoliata, unaware that by this action Scirtobaenus became again a synonym, but now of Pterolepis. These circumstances may also explain why the second species of Scirtobaenus, S. lusitanicus Bolivar 1899 can be found under Rhacocleis, with grallata under Pterolepis.
Acknowledgments
We are very grateful to Dr. Klaus Gerhard Heller, Dr. David Ragge and one referee for their comments on this paper. We express our warm appreciation to our family members, Dominique Willemse and Tjeerd Blauw (Middelburg, The Netherlands) and Manuel Willemse and his son Joost Willemse (New Orleans, USA) for their unfailing enthusiasm and help in collecting during our joint field trips. Many thanks also to Michèle Lemonnier-Darcemont (Callian, France) who provided us material of Rhacocleis poneli. For examination of the leg armature of material in their collections, many thanks are also due to the following colleagues: Battal Çiplak (Antalya, Turkey), Paolo Fontana (Isola Vicentina, Italy), Antonio Galvagni (Rovereto, Italy), Klaus-Gerhard Heller (Magdeburg, Germany), Roy Kleukers (Leiden, The Netherlands) and Jos Tilmans (Gouda, The Netherlands).
References
Fig 1. Schematic draft of the ventral side of the tip of the hind tibia in Pterolepis Rambur 1839 and Rhacocleis Fieber 1853, showing transitional forms (2–4) between what might be called (1) ‘typical’ Pterolepis with four spurs (A & B = pair of outer spurs and c & d = pair of inner spurs) and (5-8) ‘typical’ Rhacocleis with 2 spurs (A & B only, c & d lacking).
Fig. 2.
Schematic draft of the upper side of the fore tibia in Pterolepis Rambur 1839 and Rhacocleis Fieber 1853, showing the inner margin ranging from unarmed to armed with 3 spurs. The most distal spur of the outer margin is the apical spur often used in traditional classification.
Table I. Checklist of taxa of Pterolepis Rambur 1839 and Rhacocleis Fieber 1853. Columns: A, traditionally classified under these genera, based on the number of ventral inner spurs of the apex of the hind tibia (spurs c & d, as in 1–4 of Fig. 1); B, approximate distribution; C, number (n) of studied specimens; D, depositories of studied material (abbreviated as: C (B. Çiplak), F (P. Fontana), G (A. Galvagni), H (Kl.-G. Heller), K (R. Kleukers), T (J. Tilmans), W (Willemse) or other source of information; E, minimum and maximum number of observed ventral inner spurs of the tip of the hind tibia and their average number per hind tibia.
Table I. Continued
Table 2.
Checklist of presently recognised taxa of Pterolepis Rambur 1839 and Rhacocleis Fieber 1853 (Otte et.al. 2004). Columns: A, traditionally classified; B, approximate distribution; C, number (n) of studied specimens; D, depositories of studied material (abbreviated as: C (B. Çiplak), F (P. Fontana), G (A. Galvagni), H (Kl.-G. Heller), K (R. Kleukers), T (J. Tilmans), W (Willemse) or other source of information; E, minimum and maximum number of observed spurs, if any, at the upper inner (= dorsal anterior) margin of the fore tibiae (Fig. 2) and their average number per tibia; F, taxonomic assignment as revised from the number of spurs at the upper inner margin of the fore tibia.
Table 2.
Continued
