Tritoma
| Tritoma | |
|---|---|
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| Type species Tritoma bipustulata, adult from Kulmbach, Germany | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Clade: | Pancrustacea |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Cucujiformia |
| Family: | Erotylidae |
| Tribe: | Tritomini |
| Genus: | Tritoma Fabricius, 1775[1] |
| Type species | |
| Tritoma bipustulata Fabricius, 1775 | |
| Synonyms | |
|
Cyrtotriplax Crotch, 1873 | |
Tritoma is a large genus of beetles in the family Erotylidae, the pleasing fungus beetles. It is distributed mainly in the temperate parts of Eurasia, with a large evolutionary radiation in Japan. They are less diverse in North America (where a mere handful of species occur in the east) and the tropics (where records are scarce except for the abundant Tritoma dorsalis of Central America). Among its family, this genus is placed in subfamily Tritominae, or – in taxonomic arrangements that prefer a more comprehensive subfamily Erotylinae – in tribe Tritomini of the Erotylinae. As of 1999, over 100 species were recognized, and since then a handful of previously unknown ones has been described; however, the monophyly of Tritoma sensu lato is spurious and several species are being moved to new or revalidated genera in recent years.[2][3][4]
Description and ecology
[edit]Adult Tritoma beetles are small, generally less than one-quarter of an inch or 8 mm long and a bit more than half as wide. They have an oval body shape, widest slightly before the middle, with parabola-shaped wingtips and a blunter head. From the closely related genus Triplax, Tritoma sensu lato can be distinguished by a shorter and rounder body, with wider and more markedly tapering elytra, and long lines on the prosternum which extend forward of the attachment points of the forelegs and curve inwards towards the headward tip of the prosternum. The enigmatic and doubtfully distinct Pseudischyrus is extremely similar to Tritoma, but under a magnifying glass can immediately be recognized by their large compound eyes with huge ommatidia.[4][5]
Like many of their relatives, these beetles usually have a black-and-reddish coloration. Usually, they are mostly black; the orange-red color is typically limited to two large spots on the "shoulders" of the elytra, to the pronotum, or to the underside. While slight differences in color pattern (such as a black vs orange underside) are often diagnostic for species, some Tritoma have subspecies or color morphs that strikingly differ in the location and extent of the orange-red markings.[4][5]
Head
The head has small compound eyes have tiny ommatidia, indicating a diurnal or crepuscular lifestyle, but with overall rather little reliance on eyesight. All Tritoma adults possess file-like structures at the sides of the neck attachment, which, when the beetle wiggles its head, rub against the chitin and produce a squeaking sound; the degree of development of these structures is generally unreliable for distinguishing males and females. The epistome has a narrow but unbroken margin around the tip, which is either straight or slightly concave; a transverse stripe separates the margin from the bulk of the epistome. The "cheek" lobes below the compound eyes are vestigial, do not reach to the lower edge of the eyes, and are usually fully covered by the ends of the maxillary palps. The antenna length is less than half of the pronotal base width, with antenna segment 3 almost as long as the segments 4 and 5 together, and a "clubbed" antenna tip which is about half again as long as it is wide.[5]
The galea and lacinia of the maxilla resemble those of the related genus Triplax, except for the lack of teeth at the tip of the lacinia. The maxillary palps have an end segment that is rounded, somewhat triangular, and a bit more than half as long as it is wide. It does not seem to carry a brush, but there might be a vestigial brush hidden within a slit at the tip. The labium has a mentum that is mid-sized and fairly narrowly triangular. The labial palps end in a narrow segment with a strong bristle at the outer side and a tiny brush at the tip.[5]
Body, wings and legs
The prothorax is almost as wide at the base as the wings at their widest point. The pronotum is fairly wide and trapezoid-shaped, with the rear edge more than half again as long as the forward edge. A thin margin runs around the sides and front of the pronotum, but is absent from the rear. In each corner of the pronotum, there is a small and inconspicuous pore. The prosternum is bell-shaped, with lengthwise lines at the center margin of the leg attachments extending to the forward edge of the prosternum, sharply curving towards each other in front of the leg attachments, and in some species even meeting at the tip of the prosternum to enclose a flattened triangular central area between them.[5]
On the metasternum, the lines between the leg attachments are clearly engraved, and extend at least halfway between the rear edge of the leg attachment and the side of the metasternum. The scutellum is bluntly heart-shaped. The elytra are ornamented with regular lines of small punctuations; they also lack a distinct margin at the base, except for a very slim margin in front of the "shoulders".[5]
The attachments of each leg pair are widely separated. The tibiae are widened towards the ends, very much so in some species; their upper/outer edge is narrowed to a very thin "razor edge" towards the tip. Segment 4 of the tarsi is reduced, and attached to the upper centerside of segment 3.[5]
On the abdomen, coxal lines are present, and the intercoxal process is wide and has a cut-off or slightly rounded tip. Males and females do not have conspicuously different external abdominal structures. The aedeagus of the male genitalia resembles Pseudischyrus. The tegminal arms are firmly joined at the forward end, form a tooth-like lobe on the upper sides just in front of the basal piece, and have a narrow and almost membranous section below. The median strut does not exceed the median lobe in length. The internal sac is of varying length but tends to be short and entirely hidden within the sclerotized median lobe; in some species it is longer and protrudes from the lobe's central hole to almost half the length of the median strut. Its anterior end lacks conspicuous point-like muscle attachments, but in some species has a number of short lengthwise sclerotized stripes. The ejaculatory duct does not continue into the internal sac. The female genitalia are strikingly shortened, seeming almost vestigial in some species, but all parts are present and functional. Only the proctigeral and vulvar lobes are close to the typical size in Erotylidae; at the eighth abdominal segment, the genital tube has short and usually weakly sclerotized lines. The seminal receptacle is small, rounded, and bears a short well-sclerotized arm. Overall, sclerotization of the female genitalia varies considerably between members of this genus, and in some Tritoma the styli are shortened to barely more than half their width.[5]
Distribution and ecology
[edit]Tritoma is a mostly Eurasian genus, with about 80% of its known diversity occurring there; they are more plentiful towards the east, but their European diversity still exceeds the total number of known species outside Eurasia. Only a single species each is known so far from Australia and the Neotropics, and about a dozen from sub-Saharan Africa; the number of North American species is not definitely resolved, but probably just a handful, all of which occur in the more humid regions to the east of the 100th meridian west.[5]
Some Tritoma species consume euagaric mushrooms, staying concealed amidst the gills as they feed.[6] Some feed on mushrooms growing from dead trees, as well as mycorrhizae on living roots.[7] Unlike Triplax, which are often encountered in large groups on a single mushroom, Tritoma typically associate only in small numbers. Larvae and pupae of several species have been studied.[5]
One of the most common pleasing fungus beetles in Europe, T.bipustulata, is a black beetle with red spots which engages in autohaemorrhaging as a defensive behavior.[8]
Taxonomy
[edit]Molecular analysis suggests that Tritoma in its traditional circumscription is paraphyletic, and even the few North American species seem to represent at least two well-distinct genera: The lineage containing the uniformly dark-winged T.erythrocephala and T.unicolor appears to be far more closely related to the iridescent Spondotriplax antennalis from New Guinea than to "T."pulchra with bicolored wings; the latter appears as sister to an unidentified species which resembles a member of the Neotropical genus Mycotretus but does not seem to be closely related to Mycotretus scitulus.[6] Consequently, species such as "T."consobrina and "T."pulchra are often moved to the mostly Northeast Asian genus Aporotritoma nowadays, while "T."sanguinipennis is placed in Rotitma, likewise mainly Asian. But more research into the phylogeny of these beetles is needed to come to a robust conclusion on the most appropriate taxonomic treatment. Earlier authors had already noted that North American Tritoma sensu stricto usually feed on gilled fungi, while "T."pulchra and "T."sanguinipennis are typically found on polypores.[4]
Also, the enigmatic North American genus Pseudischyrus is so similar to certain Tritoma species even in the details of its genital anatomy that its distinctness requires verification; it probably also belongs into Tritoma sensu lato.[5]
The only established synonym of genus Tritoma, Cyrtotriplax, is not available to use for split-off genera. It was proposed by George Crotch in 1873 to replace Tritoma. That name had been first used in Étienne Geoffroy's 1762 Histoire abrégée des Insectes for the genus commonly called Mycetophagus from the late 18th century onwards – these are hairy fungus beetles, superficially similar but not particularly closely related to the pleasing fungus beetles described as Tritoma by Johan Fabricius in 1775. This mix-up caused considerable misunderstanding among coleopterologists throughout the 19th and 20th century, until the ICZN in 1994 fixed Fabricius' publication as the official establishment of the genus and invalidated Geoffroy's description, conserving the use of Tritoma for the pleasing fungus beetle and Mycetophagus for the hairy fungus beetle. Cyrtotriplax, which used T.bipustulata as its type species just like Fabricius' Tritoma does, thus became an objective synonym, and unavailable for any split-off genera.[1]
Species
[edit]
This species list is provisional; several species listed here would probably warrant placement in another genus.
- Tritoma acuminata Mader, 1941[9]
- Tritoma alternata Arrow, 1921 (1922)[9]
- Tritoma amethystina Deelder, 1942[9]
- Tritoma andoi Narukawa, 2003[10]
- Tritoma angulata Say, 1826
- Tritoma arrowi Mader, 1934 (= T.ornata Arrow, 1921, nec Casey, 1916)[9]
- Tritoma asahinai Nakane, 1950[9][10]
- Tritoma atrata Lewis, 1887[11]
- Tritoma atriceps Arrow, 1921 (1922)[9]
- Tritoma atripennis (Gorham, 1885)[verification needed][9]
- Tritoma atriventris LeConte, 1847 (disputed)
- Tritoma aulica (Horn, 1871)[3] (disputed)
- Tritoma aurantica Arrow, 1925[9]
- Tritoma basimaculata Kuhnt, 1908[9]
- Tritoma biguttata (Say, 1825) – two-spotted tritoma (= T.affinis, T.basalis, T.caseyi, T.carolinae, T.nigripennis Casey, 1916, nec Motschulsky, 1858, T.pinorum)
- Tritoma biplagiata (Lewis, 1887) (= T.solivaga Yasumatsu, 1937 nec Lewis, 1887)[9][10]
- Tritoma bipustulata Fabricius, 1775 (= T.bicolor, T.bimaculata, T.humeralis (Marsham, 1802) non Fabricius, 1801, T.incerta, T.pulchra (Reitter, 1887) non Say, 1826)[9]
- Tritoma bisignata Chûjô, 1967[9]
- Tritoma bivunculata Heller, 1918 (1920)[9]
- Tritoma cenchris (Lewis, 1887)[9][10]
- Tritoma centralis (Lewis, 1887)[9][10]
- Tritoma cribripennis Arrow, 1926[9]
- Tritoma crotchi (Chûjô, 1968)[9]
- Tritoma digitalis Arrow, 1925[9]
- Tritoma discaloides Nakane, 1986 (= T.discalis Nakane, 1986 nec Chûjô, 1969)[9][10]
- Tritoma dorsalis Gorham, 1888[12]
- Tritoma elegans Arrow, 1928[9]
- Tritoma endomychus Heller, 1918 (1920)[9]
- Tritoma excellens Arrow, 1925[9]
- Tritoma eximia Arrow, 1925[9]
- Tritoma erythrocephala Lacordaire, 1842 – red-headed tritoma (= T.flavipes Lacordaire, 1842 (non Panzer, 1792: preoccupied); disputed)
- Tritoma fasciata Chûjô, 1941[3][9]
- Tritoma felix Arrow, 1925[9]
- Tritoma flavipes Panzer, 1792[3][verification needed]
- Tritoma fulva (Reitter, 1879)[9]
- Tritoma gressitti (Chûjô, 1968)[3][9]
- Tritoma hakusanensis Sasaji & Hoshina, 2003[10]
- Tritoma humeralis Fabricius, 1801
- Tritoma imugina Heller, 1923[9]
- Tritoma indica (Crotch, 1876)[9]
- Tritoma infanta Arrow, 1925[9]
- Tritoma kanekoi Araki, 1943[3][9]
- Tritoma karahutonis Chûjô, 1941[9]
- Tritoma kensakui Chûjô, 1955[9][10]
- Tritoma kubotai Narukawa, 1994[10]
- Tritoma kuhnti (M.Chûjô & M.T.Chûjô, 1990) (= T.atripennis Kuhnt, 1909, nec Gorham, 1885)[9]
- Tritoma kurinoensis Nakane, 1982[9][10]
- Tritoma lagunae Heller, 1918 (1920)[9]
- Tritoma lateripunctata Mader, 1936[9]
- Tritoma latifascia Heller, 1918 (1920) (= T.helleri)[9]
- Tritoma latifasciata (Lewis, 1887) (= T.basalis (Lewis, 1887) non Lacordaire, 1842, T.lewisiana)[9][10]
- Tritoma laxicornis Arrow, 1925[9]
- Tritoma lini (Chûjô, 1968)[9]
- Tritoma lobicollis Arrow, 1925[9]
- Tritoma lobisternum Arrow, 1925[9]
- Tritoma loochooana (Chûjô, 1969)[9][10]
- Tritoma maackii (Crotch, 1876)[9]
- Tritoma maculifrons (Lewis, 1887)[9][10]
- Tritoma malaisei Arrow, 1939[9]
- Tritoma marginicollis Chûjô, 1967[9]
- Tritoma melanopa Arrow, 1925[9]
- Tritoma metasobrina Chûjô, 1941[3][9]
- Tritoma michitakai Chûjô, 1960[9][10]
- Tritoma mimetica (Crotch, 1873)
- Tritoma miyatai Narukawa, 2010[10]
- Tritoma nigribasis Arrow, 1925[9]
- Tritoma nigripes Heller, 1923[9]
- Tritoma nigrobasalis Heller, 1918 (1920)[9]
- Tritoma nigropicta Arrow, 1925[9]
- Tritoma nigropunctata (Lewis, 1887)[9][10]
- Tritoma nilgiria Arrow, 1925[9]
- Tritoma niponensis (Lewis, 1874)[verification needed][9][11][10]
- Tritoma obscura (Gorham, 1896)[verification needed][9]
- Tritoma octonotata (Bedel, 1874)[9]
- Tritoma octopunctata Bedel, 1874[11]
- Tritoma okadomei (Chûjô, 1974)[9]
- Tritoma osawai Nakane, 1981[9][10]
- Tritoma otaitoensis Nakane, 1961[9][10]
- Tritoma ozakii Narukawa, 2000[10]
- Tritoma pallidicincta (Lewis, 1887)[9][10]
- Tritoma pantherina (Lewis, 1887)[9][10]
- Tritoma picta Arrow, 1926[9]
- Tritoma pulchella Fabricius, 1789[9]
- Tritoma quatei (Chûjô, 1968)[9]
- Tritoma quinquemaculata Mader, 1941[9]
- Tritoma recurrens Arrow, 1925[9]
- Tritoma sasajii Narukawa, 2001[10]
- Tritoma scheerpeltzi Mader, 1955[9]
- Tritoma scutigera Arrow, 1925[9]
- Tritoma shibatai (Chûjô, 1969)[9][10]
- Tritoma shimoyamai Chûjô & Nakane, 1950[9][10]
- Tritoma shirakii Chûjô, 1936[3][9]
- Tritoma senegalensis (Crotch)[verification needed][13]
- Tritoma sobrina (Lewis, 1887) (= T.consobrina (Reitter, 1896) non Lewis, 1874)[9][10]
- Tritoma solitaria Arrow, 1921[9]
- Tritoma spenceri (Chûjô, 1968)[9]
- Tritoma standhali (Chûjô, 1968)[9]
- Tritoma subbasalis (Reitter, 1896)[verification needed] (= T.consobrina (Reitter, 1887) non Lewis, 1874, T.jakowlewi, T.sibirica)[9][11]
- Tritoma sungkangensis Nakane, 1966[3][9]
- Tritoma taiwana Chûjô, 1936 (= "T.atripennis" Miwa, 1931, nec Gorham, 1885: nomen nudum)[3][9][10]
- Tritoma takahashii Nakane, 1966[9][10]
- Tritoma takakurai Nakane, 1979[9][10]
- Tritoma takasagona Chûjô, 1941[3][9]
- Tritoma tenebrosa Fall, 1912 – darkling tritoma
- Tritoma testakeicornis Heller, 1918 (1920)[9]
- Tritoma towadensis Chûjô, 1952 (=T.yachiensis)[9][10]
- Tritoma toyoshimai Narukawa, 2010[10]
- Tritoma triguttata Heller, 1918 (1920)[9]
- Tritoma tripartiaria (Lewis, 1887)[9][10]
- Tritoma unicolor Say, 1826
- Tritoma uniplagiata Nakane, 1983[9][10]
- Tritoma viridipennis Arrow, 1925[9]
- Tritoma vitticollis Arrow, 1921 (1922)[9]
- Tritoma wittmeri (Chûjô, 1975)[9]
- Tritoma yamazii Chûjô, 1941[3][9]
- Tritoma yiei Nakane, 1966[3][9]
_Scudder_1890_Pl7_Fig30.png)
"Tritoma livida", named by Jean Lacordaire in 1842, is an individual caught soon after emerging from the pupa; it was misidentified as a new species because it had not yet developed its mature coloration. Most likely, it belongs to either T.biguttata affinis or to T.angulata.[5]
A supposed Tritoma species from Isla de Mona near Puerto Rico collected by J. A. Ramos in the early 20th century is actually a species of the monommatine beetle genus Hyporhagus. These deceptively resemble certain erotylid beetles (such as Tritoma) in overall appearance, but actually belong to another branch of Cucujiformia. With the proposed occurrence of "Tritoma sellata" on Cuba apparently being in error too, as of 2009, no verified Tritoma records were known from the Caribbean offshore islands.[14]
In addition, a fossil Erotylidae beetle described originally as Mycotretus binotata by Samuel Scudder in 1878 has been assigned to Tritoma due to its great resemblance to "T."sanguinipennis; it would probably belong to Rotitma if "T."sanguinipennis is validly placed there. Its specimen MCZ 4183 was found in the Lake Gosiute Green River Formation of Wyoming and originally assumed to be of Oligocene age; today, it is assumed to have been lived somewhat later, in the Early Eocene roughly 50 million years ago.[15]
References
[edit]
- 1 2 International Commission On Zoological Nomenclature (1994). "Opinion 1754. Histoire abrégée des insectes qui se trouvent aux environs de Paris (Geoffroy, 1762): some generic names conserved (Crustacea, Insecta)". Bulletin of Zoological Nomenclature. 51 (1): 58–70.
- ↑ "Tritoma Genus Information". BugGuide.net. Retrieved 2018-04-25.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 "Tritoma Fabricius, 1775". GBIF. Retrieved 2026-06-30.
- 1 2 3 4 Goodrich, Michael A. and Springer, Charles A. (1999): The Pleasing Fungus Beetles (Coleoptera: Erotylidae) of Nebraska. Transactions of the Nebraska Academy of Sciences 25: 53-71.Fulltext
- 1 2 3 4 5 6 7 8 9 10 11 12 Boyle, Wilford Wayne (1956): A revision of the Erotylidae of America north of Mexico (Coleoptera). Bull. AMNH 110: 61-172. PDF fulltext
- 1 2 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.] Systematic Entomology 29(2): 173–87. PDF fulltext
- ↑ Skelly, P. E. Pleasing Fungus Beetles, Pseudischyrus, Tritoma, Megalodacne, Ischyrus spp. (Insecta: Coleoptera: Erotylidae). EENY-091. Entomology and Nematology. Florida Cooperative Extension Service. University of Florida IFAS. 1999.
- ↑ Drilling, K. and K. Dettner. (2010). First insights into the chemical defensive system of the erotylid beetle, Tritoma bipustulata. Chemoecology 20(4), 243–253.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 Chûjô, Michio, 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.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 甲虫の自然図鑑 (Beetles in Nature): マエグロチビオオキノコ Tritoma centralis (Lewis, 1887)マエグロチビオオキノコ [in Japanese]. Retrieved 2026-06-30.
- 1 2 3 4 Wikispecies: Tritoma. Retrieved 2026-06-30.
- ↑ Alvarenga, Moacyr (1994): Catálogo dos Erotylidae (Coleoptera) Neotropicais. [Catalogue of Neotropical Erotylidae (Coleoptera). Portuguese with English abstract.] Revista Brasileira de Zoologia 11(1): 1–175. doi:10.1590/S0101-81751994000100001.
- ↑ Skelley, Paul E. (1998): A Catalogue of the Crotch Collection of Erotylidae (Coleoptera). Ann. Zool. 48(1/2): 1-44. PDF fulltext
- ↑ Skelley, Paul E. (2009): Pleasing fungus beetles of the West Indies (Coleoptera: Erotylidae: Erotylinae). Insect.Mund. 82: 1–94. PDF fulltext
- ↑ Scudder, Samuel H. (1890): The Tertiary insects of North America: 502–503. United States Geological Survey of the Territories, Washington BHL fulltext