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Mycotretus

From Wikipedia, the free encyclopedia

Mycotretus
Adult Mycotretus sexoculatus, São Bernardo do Campo, Brazil
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Arthropoda
Clade: Pancrustacea
Class: Insecta
Order: Coleoptera
Suborder: Polyphaga
Infraorder: Cucujiformia
Family: Erotylidae
Tribe: Tritomini
Genus: Mycotretus
Lacordaire, 1842
Type species
Erotylus lesueuri
Lacordaire, 1842
Synonyms

Lybas Dejean, 1836 ("1837"; unavailable)
Mycotretus Chevrolat, 1837 (lapsus)
Mycotretus Dejean, 1836 ("1837"; unavailable)

Mycotretus is a large genus in the pleasing fungus beetle family (Erotylidae). They are small, oval beetles, and often very colorful and boldly patterned in yellowish, orange-red to chestnut-brown, and black hues; historically, they were popular with insect collectors. 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.[1][2]

These beetles are found throughout the Neotropics except on high mountain ranges. Some isolated records from temperate North America presumably refer to introduced specimens. One species (M.nigromanicatus) ranges as far north as the Chiricahua Mountains of Arizona, USA, while in the south of the genus' range, several species are found in Paraguay and northern Argentina. While some species, such as M.ornatus, M.pygmaeus and M.scitulus, occur almost across the entire range of the genus, many are restricted to a single range of hills or to one area bordered by large rivers, with Mexico and the Amazon Basin having the highest diversity of Mycotretus.[3][4] Like some of their relatives, they do not eat mainly polypores (shelf fungi) as most pleasing fungus beetles do, but prefer gilled Agaricales fungi; unlike in the close relative Pselaphacus, larvae of Mycotretus species feed individually and do not receive parental care.[5]

This genus has a convoluted nomenclatural history involving the related genera Ischyrus and Lybas.[6] In addition, its delimitation against Mycomystes was long disputed and as of 2023 is still not fully resolved,[2] and it possible that some little-known genera such as Haematochiton turn out to properly belong into Mycotretus.[7]

Description

[edit]

Mycotretus are small beetles, typically less than 1 cm long as adults, and usually only about half that size at most. Their body is elliptical, sometimes with a slightly blunter head, smoothly rounded on all sides, fairly flat-backed, and twice as long as it is wide or slightly longer. They are usually two- to four-colored, in a blackish and one or two orange-yellow to reddish-brown hues, and sometimes some yellowish-white; the exact pattern varies according to species, but typically is spotted or striped.[7]

Head
The head generally seems to lack file-like structures for stridulation, and has no constriction between the rather small compound eyes. The individual ommatidia are also small; this genus is probably diurnal or crepuscular, but generally does not seem to rely on eyesight much. The epistome is unmargined, due to the ocular striae at most barely reaching the antenna insertion points, and ends in an almost straight edge with a slight concave indentation. The antenna length is about two-thirds of the pronotal base width or a bit more, with antenna segment 3 almost as long as the segments 4 and 5 together, and a "clubbed" antenna tip. This is usually formed by the last 4-5 segments and gradually widens; in some it only consists of 3 segments, with the initial one (segment 9) abruptly wider than the preceding.[7]

The maxillary palps have an end segment that is rounded and shortened (in some species only one-third as long as it is wide), and does not carry a brush; the maxillary lacinia at least in some species lack teeth at the tip. The labium has a large and rounded or weakly pentagonal mentum with a weakly pointed tip, and palps which end in a comparatively small hatchet-shaped segment with a strong bristle at the outer side and a sharply cut-off tip which bears a tiny brush. The postmandibular lobes are so little developed as to be invisible in most species.[7]

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 approximately square- to trapezoid-shaped, with the forward edge about the same length as the rear edge or slightly shorter, and the pronotal length somewhat smaller than the forward edge; the sides curve towards the forward end. A thin margin runs all around the pronotum, but may be less well developed on the front edge between the compond eyes, unlike in Haematochiton where the pronotal margin is clearly absent between the eyes. There are no conspicuous pores in the corners of the pronotum. The tip of the prosternum is either compressed into a pitcher-like lip, or vertically evenly rounded; the lengthwise lines at the center margin of the leg attachments extend forward of these a tiny bit or not at all, are strongly engraved, and run almost parallel.[7]

On the mesosternum, the lines between the leg attachments are scarcely visible or entirely absent; on the metasternum they are more clearly engraved. The scutellum is bluntly heart-shaped to pentagonal. The elytra are ornamented with regular lines of small punctuations; they also have a distinct margin at the base, which is very pronounced in some species but fairly weak in others, and does not extend all the way to the tip.[7]

The attachments of each leg pair are neither particularly close or conspicuously far away. The tibiae are not widened towards the ends. Segment 4 of the tarsi is reduced, and attached to the upper centerside of segment 3.[7]

At least in most Mycotretus (but perhaps not in all), the males, but not the females, have a conspicuous roughly punctated spot in the center of the underside of the first abdominal segment. The aedeagus of the male genitalia at least in some species strikingly resembles that of Haematochiton in having a distinctive anterior end of the internal sac, whose main body is long and may even wind around the ejaculatory duct which is also sizeable. On the other hand, the female genitalia are more reminiscent of Triplax species such as T.thoracica, with an eighth tergite which has strongly sclerotized lines along the sides, and in the centerline near the tip a deep but narrow membranous indentation.[7]

Nonwithstanding their wide distribution, considerable diversity, and conspicuous appearance, the ecology of these beetles remains almost unknown – and what is known is mostly conjectural – even today. As late as the mid-20th century, no study had been done on their larvae and pupae.[7]

Nomenclature and taxonomy

[edit]

Mycotretus is one of the largest genera in this family – possibly the second-largest; after its latest revision in 2023, when numerous supposed species were synonymized with others (in particular the highly variable Mycotretus ornatus) or moved to other genera, it still contained almost 170 accepted species.[2]

This Mexican specimen of Mycotretus lesueuri, initially named Erotylus leseuri by Chevrolat and placed in Lybas by Dejean, is the name-bearing type of its species, and thus also of the entire genus Mycotretes

The genus names Ischyrus, Lybas and Mycotretus were first published by Pierre Dejean in the second edition of his Catalogue des Coléoptères in 1836[8]; however, he attributed these names to Louis Chevrolat instead of claiming authorship himself. Dejean's catalog was a simple list of names, with no diagostic criteria or descriptions, but as he included well-known species that hat been extensively described by previous authors in each of his genera, his genera are technically valid.[6]

Jean Lacordaire in 1842 published a monograph on the pleasing fungus beetles. Therein, he also used the genus names Ischyrus, Lybas and Mycotretus, attributing them to Chevrolat just as Dejean did. However, Lacordaire placed Dejean's Lybas species in Mycotretus and re-established the genus Lybas for Lybas normalis, a species mentioned by preceding authors such as Dejean, but never validly described until Lacordaire's 1842 work. Meanwhile, most of Dejean's small Mycotretus species were moved into Ischyrus by Lacordaire, where they formed a second "division" (subgenus) distinct from the large tropical species which had already been placed in Ischyrus by Dejean.[6]

In 1873, George Crotch split genus Ischyrus, elevating Lacordaire's groups to full genus status. But he retained the name Ischyrus for the second group, which had been treated as Mycotretus by Dejean. The first group, Dejean's Ischyrus, was named Megischyrus by Crotch. For his remaining Ischyrus, Crotch designated Olivier's Erotylus quadripunctatus as type species. As he only referred back to Lacordaire, Crotch overlooked that Dejean had included this species in Mycotretus, preventing its use as type species of Ischyrus.[6]

However, Crotch failed to designate a type species for Mycotretus. W.W.Boyle attempted to correct this in 1956, and selected the beetle described as Erotylus leseuri by Chevrolat in 1935. But like Crotch with his Ischyrus type species, Boyle did not note that Dejean had included this species in his genus Lybas at the time when he established Mycotretus, making Boyle's type designation invalid.[6]

Subsequent authors applied the genus names as proposed by Crotch and Boyle, until Moacyr Alvarenga in 1965 revalidated Dejean's Ischyrus with E.undatus as type species, making Megischyrus a junior objective synonym and invalidating it. For the second group, containing most of Dejean's Mycotretus, Alvarenga established the genus Micrischyrus, with E.quadripunctatus as type species to exactly replace Crotch's Ischyrus which had become a junior homonym by the abolishment of Megischyrus, and likewise invalidated. However, almost all Erotylidae research at that time was published in English, with Japanese and German having some minor relevance due to prolific experts Michio Chûjô and Kurt Delkeskamp, whereas Alvarenga published in Brazilian Portuguese and his nomenclatural acts appeared in the then little-known zoological bulletin of the Federal University of Paraná (now Acta Biologica Paranaense). Consequently, unaware of Alvarenga's proposed solution to a problem they often were not even aware of in the first place, other erotylid researchers continued to apply Crotch's nomenclature. As for Mycotretus, its authorship was mistakenly referred by Alvarenga to Chevrolat, 1837, with M.ornatus (under its original name Erotylus ornatus) as alleged type species.[6]

To resolve this situation, Paul E. Skelley and Michael A. Goodrich in 1994 petitioned the ICZN to rule Dejean's descriptions as invalid; this would preserve the prevailing genus assignments. In 1996, the ICZN agred to this proposal, establishing Lacordaire as the author of Mycotretus due to Crotch's and Boyle's revalidation of his genus. This also permitted E.leseuri to be type species of Mycotretus, courtesy of Lacordaire having moved it there.[9]

Species

[edit]
Mycotretus centralis in Santa Rosa de Calamuchita, Argentina
Mycotretus duodecimguttatus in Panguana, Peru
Mycotretus fallax in Iguaçu National Park, Brazil
Mycotretus marginicollis in Cruz Alta, Brazil
Mycotretus mycetophagoides in San Roque de Cumbaza, Peru
Mycotretus mycetophiloides specimen from Tefé, Brazil
Mycotretus ornatus in Buenos Aires, Argentina
Mycotretus pecari in El Valle de Antón, Panama
Mycotretus psittacus in Tinguá, Brazil

A supposed Mycotretus 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 Mycotretus) in overall appearance, but actually belong to another branch of Cucujiformia. As of 2009, no species of Mycotretus were known from the Caribbean offshore islands.[10]

In addition, the names "Mycotretus bruchi" and "M.unguicularis", despite having been attributed to Bruch, 1915, were never validly established; they are nomina nuda. The former has been identified as Mycotretus trifasciatus, while the latter is still undeterminable.[2]

Formerly placed here

[edit]
Mycomystes apicalis was mistaken for a new species of Mycotretus by several 19th-century experts

Several species traditionally placed in Mycotretus have eventually turned out to belong to other genera:[2]

The Ischyrus species of Lacordaire's "second division", placed by Dejean in Mycotretus, are I.incertus, I.interruptus, I.laetus, I.patruelis (="M." similis), I.quadripunctatus (="M." humeralis, "M." subcylindricus, "M." variegata), I.scriptus (= "M." affinis), and I.variabilis.[2]

References

[edit]
  1. ↑ "Genus Mycotretus". iNaturalist. Retrieved 2026-06-15.
  2. 1 2 3 4 5 6 Pecci-Maddalena, Italo Salvatore de Castro; Lopes-Andrade, Cristiano; Skelley, Paul (2023). "Catalogue of Mycotretus Lacordaire, 1842 (Coleoptera: Erotylidae: Tritomini): An annotated, illustrated and historical approach". European Journal of Taxonomy (876): 2149. Bibcode:2023EJTax.876.2149P. doi:10.5852/ejt.2023.876.2149.
  3. ↑ "Mycotretus Lacordaire, 1842". GBIF. Retrieved 2026-06-15.
  4. ↑ Alvarenga, Moacyr (1994). "Catálogo dos Erotylidae (Coleoptera) Neotropicais". Revista Brasileira de Zoologia. 11: 1–175. doi:10.1590/S0101-81751994000100001.
  5. ↑ 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. doi:10.1111/j.0307-6970.2004.00242.x PDF fulltext
  6. 1 2 3 4 5 6 Skelley, Paul E.; Goodrich, Michael A. (1994). "Ichyrus Lacordaire, 1842, Lybas Lacordaire, 1842, Mycotretus Lacordaire, 1842 and Megischyrus Crotch, 1873 (Insecta, Coleoptera): Proposed Conservation" (PDF). The Bulletin of Zoological Nomenclature. 51: 128–132. doi:10.5962/bhl.part.7176.
  7. 1 2 3 4 5 6 7 8 9 Boyle, Wilford Wayne (1956): A revision of the Erotylidae of America north of Mexico (Coleoptera). Bull. AMNH 110: 61-172. PDF fulltext
  8. ↑ Sometimes erroneously dated to 1837.
  9. ↑ ICZN (1996): Opinion 1824. Ischyrus Lacordaire, 1842, Lybas Lacordaire, 1842, Mycotretus Lacordaire, 1842 and Megischyrus Crotch, 1873 (Insecta, Coleoptera): conserved. Bull. Zool. Nomenclat. 53(1): 54-56. Fulltext
  10. ↑ Skelley, Paul E. (2009): Pleasing fungus beetles of the West Indies (Coleoptera: Erotylidae: Erotylinae). Insect.Mund. 82: 1-94. PDF fulltext
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