Stetholiodes Fall

WHEELER, QUENTIN D. & MILLER, KELLY B., 2005, Slime-Mold Beetles Of The Genus Agathidium Panzer In North And Central America, Part I. Coleoptera: Leiodidae, Bulletin of the American Museum of Natural History 2005 (290), pp. 1-95 : 34-37

Stetholiodes Fall

Stetholiodes Fall, 1910: 4 (Type species: Stetholiodes laticollis Fall, 1910 , by monotypy); Blatchley, 1910; Wheeler, 1981; Newton, 1982, 1998; Angelini and de Marzo, 1983, 1987b; Perkovskii, 1990.

Agathodes Portevin, 1926: 80 (Type species: Agathodes striatipenne Portevin, 1926 , by monotypy) preoccupied, nec Agathodes Guénée, 1854 , Lepidoptera .

Agathidiodes Portevin, 1926: 169 (new name for Agathodes Portevin, 1926 ); Newton, 1983 (synonymized with Stetholiodes ).

DISCUSSION: The genus Stetholiodes was described from northern Indiana by Fall (1910), based on material collected from moss ( Blatchley, 1910). Wheeler (1981) redescribed S. laticollis Fall and discussed this single North American member of the genus. Additional species are known from Asia and eastern Europe ( Angelini and de Marzo, 1987b). Monophyly of the genus has not been firmly established. Habits remain unknown, though slime­mold associations in related genera suggest similar relationships in this taxon.

Agathidium Panzer

Volvoxis Kugelann, 1794: 535 (Type species: Tetratoma globosa Herbst, 1792 (= A. seminulum ( Linnaeus, 1758) , by subsequent designation of Newton, 1998), not preoccupied by Volvox Linnaeus, 1758 , Chlorophyta. NOMEN OBLITUM.

Agathidium Panzer, 1797: 13 (Type species: Tetratoma globosa Herbst, 1792 (= Silpha seminulum Linne´, 1758, by monotypy); Illiger, 1798; Palisot de Beauvois, 1817; Sturm, 1807; Stephens, 1829, 1839; Leach, 1832; Erichson, 1845; Redtenbacher, 1845, 1849, 1858, 1874; Fairmaire and Laboulbene´, 1854; Jacquelín du Val, 1857; Thomson, 1859, 1862; LeConte, 1861; Brisout, 1872; Cox, 1874; Seidlitz, 1891; Horn, 1880; LeConte and Horn, 1883; Fowler, 1889; Everts, 1899; Ganglbauer, 1899; Stierlin, 1900; Schaufuss in Calwer, 1916; Jacobson, 1910; Blatchley, 1910; Kuhnt, 1913; Portevin, 1914, 1926, 1927, 1929; Barthe, 1920 –1922; Hansen, 1922a; Houlbert, 1922; Hatch, 1929a, 1929b, 1957; Joy, 1932; Fall, 1934; Javorek, 1947; Horion, 1949; Hlisnikovský, 1964; Arnett, 1971; von Peez, 1971; Hendrichs, 1980; Angelini and De Marzo, 1984, 1987a, 1987b, 1988, 1990, 1995; Angelini, 1984, 1988, 1990; Nunberg, 1987; Wheeler, 1987, 1990a; Newton, 1998; Angelini and Peck, 2000; Peck et al., 2000. NOMEN PROTECTUM.

Agathidium Illiger, 1798: 81 , unnecessary replacement name for Volvoxis Kugelann, 1794 .

Chaetoceble Sainte­Claire­Deville, 1899: 292 (Type species: Agathidium pilosum Sainte­Claire­Deville, 1899, by original designation) (subgenus).

Cyphoceble Thomson, 1859: 59 (Type species: Anisotoma staphylaeum Gyllenhal, 1810 (= A. nigrinum Sturm, 1807 , by original designation) (subgenus).

Saccoceble des Gozis, 1886: 17 (Type species: Agathidium discoideum Erichson, 1845 , by original designation) (synonym of Cyphoceble ).

Euryceble Hlisnikovsky´, 1964: 123 (Type species: Agathidium antennatum Hlisnikovsky´, 1964, by original designation) (subgenus).

Macroceble Angelini, 1993: 30 (Type species: Agathidium shermathangense Angelini and De Marzo, 1981 ) (subgenus).

Microceble Angelini and De Marzo, 1986: 439 (Type species: Agathidium grouvellei Portevin, 1907 , by orginal designation) (subgenus).

Neoceble des Gozis, 1886:16 (Type species: Agathidium marginatum Sturm, 1807 , by original designation) (subgenus).

Stigmoceble Hlisnikovský 1964: 119 (Type species: Agathidium longicorne Portevin, 1908 , by original designation); Angelini, 1986 (synonymized with Neoceble ).

Rhabdoelytrum Hlisnikovsky´, 1964:31 (Type species: Agathidium sexstriatum Horn, 1880 , by original designation) (subgenus).

DIAGNOSIS: Agathidium may be distinguished from other Agathidiini in North and Central America by the following combination of characters: antennal club usually distinctly 3­segmented (5­segmented in a few taxa, including A. rusticum Fall ); anterior clypeal margin usually not extending beyond anterolateral margins of frons (extending beyond frons in the A. sexstriatum group and several species of the A. pulchrum and A. concinnum groups); supraocular carina extending from margin of clypeus or clypeal region posteriorly to well behind eye delimiting a postocular temporum that may be short and inconspicuous or long and very conspicuous; elytral punctation usually confused or absent, occasionally serial, but with fewer than nine series and series often obscured by dense confused punctures between; prothorax convex; elytra usually convex, sometimes dorsoventrally compressed.

DISCUSSION: The name Agathidium is derived from ‘‘ agathidion ’’, Greek for ‘‘small ball’’, and is quite appropriate for many species of the genus which have broad convex bodies capable of rolling into compact, balllike shapes when disturbed.

A complete bibliography and synonymic list for Agathidium is provided by Newton (1998) along with a discussion of some nomenclatural problems including the observation that the original name for this taxon, Volvoxis , is not a homonym as supposed. Volvoxis is the oldest name for the genus, and historically the International Code of Zoological Nomenclature (the Code) would have required either resurrection of the name Volvoxis for this genus or a special ruling by the Commission for conservation of the junior name Agathidium and suppression of Volvoxis . However, according to article 23.9 of the newest Code ( ICZN, 1999), the prevailing usage of a junior name may be maintained when the senior name has not been used as a valid name after 1899 (to our knowledge true of Volvoxis ) and the junior name has been used as a presumed valid name in at least 25 works published by at least 10 authors in the preceding 50 years and a span of not less than 10 years (true of Agathidium , see bibliography above). Therefore, of the two names Volvoxis Kugelann and Agathidium Panzer , the second is the valid name.

Agathidium has historically been divided into subgenera, several of which were proposed as recently as the 1980s and 1990s ( Angelini, 1993; Angelini and De Marzo, 1986). Subgenera recognized for the Palearctic fauna can be used to organize the Nearctic fauna, though with considerable difficulty in some cases, and they may be identified using Angelini’s (1995) key. However, because our fauna remains poorly known, and monophyly of the subgenera as currently classified remains equivocal, we have decided to not recognize subgenera and instead arrange the species treated here into informal species groups. Our proposed species groups would loosely belong to previously recognized subgenera in the following way: A. brevisternum group = A. ( Neoceble ) des Gozis; A. oniscoides group = A. ( Agathidium ); A. revolvens group = A. ( Neoceble ) (centered around A. nigripenne Fabricius ); A. concinnum group = A. ( Cyphoceble ) Thomson; A. pulchrum group = A. ( Neoceble ). Our A. iota and A. compressidens species groups do not appear to fit well into any of the described subgenera.

Especially problematic are those species described by Horn and later placed in their own subgenus, A. ( Rhabdoelytrum ), by Hlisnikovský (1964). According to our scheme of species groups, the A. sexstriatum group would belong to this subgenus. According to the characters used by Angelini and de Marzo (1987b) to distinguish Agathidium from Stetholiodes , the species of A. ( Rhabdoelytrum ) would key to Stetholiodes . For now, these controversial and primitive forms are retained in Agathidium although there is merit in considering a different combination. Considering only our fauna, such a combination would appear to make Agathidium species monophyletic, based in part on the relatively excavate clypeus or clypeal region, while making monophyly of Stetholiodes uncertain and based primarily on symplesiomorphic character states.

There have been two cladistic analyses including members of this tribe. Considering the world genera of the tribe, and a small data set of adult characters, Angelini and Peck (2000) proposed the following relationships: ( Anisotoma + ( Amphicyllis + ( Liodopria + ( Cyrtoplastus + ( Sphaeroliodes + ( Stetholiodes + ( Afroagathidium + ( Pseudoagathidium + ( Besuchetionella + ( Agathidium ))))))))). Relationships among non­ Agathidium taxa are beyond the scope of this work, but see Miller and Wheeler (in press) for a discussion of their conclusions.

Kilian (1998) also conducted a cladistic analysis of agathidiine taxa, but one using larval instead of adult characters. She suggested synonymizing Anisotoma with Agathidium based on the conclusion that Agathidium species are nested in several places within Anisotoma . However, Kilian’s analysis was based on a relatively limited data set including only characters from larvae and only those from the relatively few species of agathidiines known from larvae (including only several species of Agathidium and Anisotoma and one species of Liodopria ). Another recent analysis by Angelini and Peck (2000) (see above) used adult characters cod­ ed from many more taxa representing a greater diversity within Agathidiini . They found a solution to the phylogeny radically different from Kilian’s (1998). Further analyses incorporating more comprehensive taxon and character sampling are likely to result in different results from each of these. Thus, we would regard any nomenclatural change based on Kilian’s (1998) phylogeny to be injudicious at this time. In addition, whereas we would agree that such a conclusion as she presents would call for synonymy of the two names, doing so would likely serve little except to make Agathidium even more heterogeneous in character combinations than it already is. We think that were Agathidium or Anisotoma eventually found to be paraphyletic, it would be more appropriate to break up these two huge groups of species into genera rather than synonymizing them.

Agathidium are sometimes misidentified in collections with the following taxa, from which they may be distinguished by characters given parenthetically: Anisotoma (fig. 41: Agathidium with head not narrowed immediately behind eye [except in some A. pulchrum and A. sexstriatum species groups] and with antennal club rarely approaching 5­ segmented); Clambidae ( Agathidium never with enlarged hind coxal plates); cybocephaline Nitidulidae ( Agathidium with front coxae conical, not transverse); acanthocerine Scarabaeidae ( Agathidium with antennae not lamellate); sphaeridiine Hydrophilidae ( Agathidium with club not so compact).

During this revision three species previously placed in Agathidium , A. cognatum Matthews, 1887: 77 , A. parile Fall, 1934: 117 , and A. parvulum LeConte, 1878: 598 , were discovered to belong to a separate genus along with several undescribed Central and South American species. These species are treated in a separate revision (Miller and Wheeler, in press).

KEY TO SPECIES GROUPS OF