Tritomini is a tribe of pleasing fungus beetles (family Erotylidae) belonging to subfamily Erotylinae. If the Erotylinae are delimited more narrowly, the Tritomini are elevated to subfamily status as Tritominae. They occur almost globally, with more than 400 species in some three dozen genera; from North America, about 35 species in 9 genera are reported.
Description Tritomini (or Tritominae) are characterized by having "clubs" at the tips of the antennae, which are composed of 3-5 distinct and widened segments; the first segment of their curved maxillary palps is longer than segments 2 and 3 together, and the end segment is wider than long. The mentum of the labium is highly variable in shape and size, but generally not wider than high; the labial palps are more or less widened at the tip, which is usually hatchet-shaped and has one conspicuous strong bristle on the outer side, and the sides of the mouth cavity form flat lobes. On the prothorax, the holes for the foreleg attachments are fully closed; halfway between the leg attachments and the rear margin of the prothorax, there is a seam between prosternum and proepimera. The joint between meso- and metasternum has a broad double knob. On the 5-segmented tarsi, the first three segments are increasingly widened, while segment 4 is reduced, attached to the upper centerside of segment 3, and firmly joined to the base segment 5.Deelder, C.L. (1942): Revision of the Erotylidae (Coleoptera) of the Leiden Museum. Zool. Meded. 24(3): 49-115. FulltextBoyle, Wilford Wayne (1956): A revision of the Erotylidae of America north of Mexico (Coleoptera). Bull. AMNH 110: 61-172. PDF fulltextDai, Cong-Chao & Zhao, Mei-Jun (2013): A new species of Scelidopetalon Delkeskamp (Coleoptera, Erotylidae) from China with a key to world species of the genus. ZooKeys 317: 81–87. (Fulltext)
The lacinia of the maxilla may have two small curved teeth at the tip (e.g. in Triplax) which are sometimes so small and close together to appear as a single tooth; or it may lack such structures entirely (e.g. in Tritoma). Up to the mid-20th century, it was assumed that all members of this group lacked lacinia teeth. Upon the discovery of this distinction,Delkeskamp, Kurt (1962): Die afrikanischen Arten der Tritomini und von 3 Gattungen der Triplacini (Col. Erotylidae). 31. Beitrag zur Kenntnis der Erotyliden. ["The African species of Tritomini, and on 3 genera of Triplacini. 31st contribution to the knowledge of erotylids." Article in German.] Dt. entomol. Z. N.F. 9(1/2): 66-125. the historical distinction between Tritomini (or Tritominae) and Triplacini (or Triplacinae) became again relevant, but whether the Triplax and Tritoma lineages should be considered distinct subtribes (or tribes, in case a subfamily Tritominae is recognized) is deferred until thorough phylogenetic studies of this group are available.
The coloration of pronotum and elytra is very diverse, with a few species even iridescent – otherwise quite rare in this family –, but eyespots are generally absent (though there are exceptions, e.g. in the vast Mycotretus assemblage).
Systematics and ecology The systematics of this tribe (or subfamily) are not fully resolved as of 2020. In addition to the relationship to the Erotylinae, the delimitation of the Tritomini versus the Xenoscelinae (or Cryptophilinae if the sensu stricto delimitation of pleasing fungus beetle subfamilies is applied), specifically the "Toramini", is not clear at all. One molecular phylogenetic study found the "Toramini" embedded within the "Tritominae", but the latter did not resolve as a clade but rather as an evolutionary grade. Since only the genus Toramus was sampled to represent the entire Xenoscelinae (or Cryptophilinae), these results require more thorough investigation.Robertson, James A.; McHugh, Joseph V. & Whiting, Michael F. (2004): A molecular phylogenetic analysis of the pleasing fungus beetles (Coleoptera: Erotylidae): evolution of colour patterns, gregariousness and mycophagy. Syst.Entomol. 29(2): 173-187. PDF fulltext
Adults and larvae of these beetles presumably eat basidiomycete fungi, as is typical for Erotylidae, but details about their ecology are known only for a few Tritomini. Even so, this group is noted for some divergences from the usual ecology of pleasing fungus beetles: some genera (such as Mycotretus, Triplax and Tritoma) do not eat mainly polypores (shelf fungi), but prefer gilled Agaricales fungi or even a more varied diet. The larvae of some species are gregarious during feeding, and parental care has been recorded in Pselaphacus.
Genera
These genera belong to the tribe Tritomini:
Afrotriplax Delkeskamp, 1965Delkeskamp, Kurt (1965): Die afrikanischen Arten der Triplacini (mit 1. Nachtrag für die afrikanischen Tritomini) (Col. Erotylidae). 34. Beitrag zur Kenntnis der Erotyliden. ["The African species of Triplacini (with 1st addendum for African Tritomini). 34th contribution to the knowledge of erotylids." Article in German.] Dt. entomol. Z. N.F. 12(1/2): 83-177. Altisessor Skelley, 2009 Amblyopus Lacordaire, 1842Chûjô, Michio & Chûjô, Michitaka (1990): A catalog of the Erotylidae (Insecta, Coleoptera) from the old world (excl. the Ethiopian region) III. Esakia 29: 1-67. PDF fulltext. Amblyscelis Gorham, 1888 Antoinettia Skelley, 2020Skelley, Paul E. (2020): A new Central American genus of pleasing fungus beetles (Coleoptera: Erotylidae) from the Ischyrus-Megischyrus complex. Insect. Mund. 804: 1–11. PDF fulltext (formerly in Ischyrus) Aporotritoma Arrow, 1925 (sometimes in Tritoma) Bancous Pic (= Rhamphidera; formerly in Rhysopaussini)Skelley, Paul E. & Alonso-Zarazaga, Miguel A. (2003): Synonymy of Rhamphidera Skelley with Bancous Pic, termitophilous fungus beetles (Coleoptera: Erotylidae). Insecta Mundi 17(1-2): 107-109. PDF fulltext Callischyrus Crotch, 1876Alvarenga, Moacyr (1994): Catálogo dos Erotylidae (Coleoptera) Neotropicais. [Catalogue of Neotropical Erotylidae (Coleoptera). Portuguese with English abstract.] Revista Brasileira de Zoologia 11(1): 1-175. . Camptotritoma Heller, 1920 Chasmatodera Arrow, 1943 Congocola Delkeskamp, 1962 Cubyrus Skelley, 2009 (formerly in Ischyrus) Cyrtomorphus Cyrtomorphoides Heller, 1920 Dactylotritoma Arrow, 1925 Epytus (= Oocyanus) Eudaemonius Lewis, 1887 (= Eutriplax Lewis, 1887) Haematochiton (= Scaeother, may belong into Mycotretus) Helcocerus Arrow, 1944 Hirsutotriplax Ischyrus Lacordaire, 1842 (= Micrischyrus) Isochyrus Kratopsis Delkeskamp, 1965 Latosia Delkeskamp Libatomorpha Heller, 1920 (= Lybatomorpha) Lybanodes Gorham, 1888 Lybas Lacordaire, 1842 (= Apolybas) Lybasia Delkeskamp, 1965 Megischyrus (= Ischyrus Dejean, 1836 ("1837"; unavailable)) Michyrus Skelley & Gasca-Álvarez, 2020 Motrita Westwood, 1883 (formerly in Tritoma) Myceporthus Skelley & Powell, 2018 (formerly in Mycophtorus) Mycolybas Mycomystes (= Mycocystes (lapsus)) Mycophtorus Lacordaire, 1842 (= Neomycotretus) Mycotretus Neotrimota Deelder, 1942 Neotriplax Lewis, 1887 Neotritoma Heller, 1920 (sometimes in Spondotriplax) Neoxestus Crotch, 1875 Notaepytus Skelley, 2009 (formerly in Epytus) Ortitma Heller, 1920 (= Cyrtotriplax Gorham, 1888 non Crotch, 1873; formerly in Tritoma) Palaeolybas Crotch, 1875Skelley, Paul E. (1998): A Catalogue of the Crotch Collection of Erotylidae (Coleoptera). Ann. Zool. 48(1/2): 1-44. PDF fulltext Phoxogenys Gorham, 1888 Pselaphacus Percheron, 1835 Pseudamblyopus Araki, 1941 Pseudamblyscelis Philipp Pseudischyrus (may belong into Tritoma) Pseudolybas Gorham, 1888 Pseudotritoma Gorham, 1888 (formerly in Tritoma) Renania Lewis, 1887 Rhodotritoma Arrow, 1925 Rhopalotriplax Deelder, 1942 Rhopalotritoma Heller, 1920 Rhynchotritoma Arrow 1920 Rotitma Chûjô, 1969 (sometimes in Tritoma) Scelidopetalon Delkeskamp, 1957 (= Petaloscelis Gorham, 1896 nec Bergroth, 1893: preoccupied, Pycnogeusteria; may belong in Pseudamblyopus) Sphaerotritoma Arrow, 1943 Spondotriplax Crotch, 1875 (= Hedista) Tetratriplax Lewis, 1887 (= Pselaphandra) Tetratritoma Arrow, 1925 Titorma Heller, 1920 Trichotritoma Arrow, 1936 Trimota Heller, 1920 (formerly in Tritoma) Triplacidea Gorham, 1901 (formerly in Tritoma) Triplax (= Paratritoma, Tritomapara) Tritoma (= Cyrtotriplax Crotch, 1873) Tritomophasma Heller, 1920 Tritomorpha M.T.Chûjô & M.Chûjô, 1987 Xalpirta Skelley & Čekalović Kušcević, 2001 (formerly in Triplax) Xenotritoma Arrow, 1923 Xestus Wollaston, 1864 (tentatively placed here) Xiphidiophora Delkeskamp, 1962 Zythonia Westwood, 1874 (= Brechmotriplax, Lophocrotaphus)
The genus Pantocryptus, formerly placed here, has turned out to be misidentified sap beetles of genus Cychramptodes.
References
Further reading