Megalodacne is a genus of fungivorous beetles in the family Erotylidae. Found in much of the world's warmer regions and in some temperate areas, it contains several dozens of species,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 but its exact delimitation has historically been much disputed and is still not entirely certain today.
Description
Adult beetles of the genus Megalodacne range in size from , making them among the larger members of the family.
Distinguishing characteristics of the genus along with other members of the subfamily Megalodacninae include large compound eyes and a lack of depressions in the "clubbed" tip of the antennae. The first three tarsus segments are slightly flattened cylinders, somewhat expending towards the tip, and of similar shape and size, while the fourth is significantly shorter and partially hidden within the third. On the underside, the first three segments have three groups of hairy pads.Heller, Karl B.M.J. (1918): Zur Klassifikation einiger afrikanischer Erotyliden. ["On the classification of some African erotylids". Article in German.] Entomologische Blätter und Coleoptera 14(4-6): 136-157. PDF fulltextWęgrzynowicz, Piotr (2002): Morphology, phylogeny and classification of the family Erotylidae based on adult characters (Coleoptera: Cucujoidea). Genus 13(4): 435–504. PDF fulltext
Species of the genus Megalodacne closely resemble members of the genera Episcapha, Episcaphula and Mimodacne (which were formerly entirely or partly included in Megalodacne). They also often look superficially similar to several other beetles since the patterns of the markings of yellow, orange, or red on the elytra (called "fascia") of Megalodacne are shared by many other beetle species.
Megalodacne adults are distinguished from the closest relatives by a combination of traits: large size and a somewhat convex back, compound eyes with large ommatidia (indicating nocturnal or crepuscular habits), a pronotum that is wider than long and has distinctly margined sides, maxillary palps with a blunt and obliquely cut-off tip segment, and an antenna "club" which never involves the seventh segment (and usually only starts with the ninth).
Among those beetles most often confused with Megalodacne is the sap beetle (Nitidulidae) genus Glischrochilus. Their native ranges overlap, making it easy to confuse them (as with Megalodacne fasciata, Megalodacne heros, and the nitulidid Glischrochilus fasciatus from eastern North America). The best way to tell them apart is by size, as sap beetles are generally small, ranging from in length. Glischrochilus reaches a maximum length of only .Glischrochilus obtusus Megalodacne on the other hand are large beetles ranging from . The elytra of the sap beetles which most resemble Megalodacne also do not cover the whole abdomen and leave the last abdominal segment(s) exposed. The elytra of Megalodacne, on the other hand, completely cover the abdomen.
Ecology Megalodacne species feed on harder bracket fungi than smaller members of the family. The fungi eaten include Ganoderma and Fomes species.
Megalodacne deposit eggs on the fungi on which they feed. Upon hatching, the larvae, like adults, also feed on the fruiting bodies of bracket fungi by burrowing into it.
There are two kinds of larvae of Megalodacne depending on the species. In some species, the larvae are elongated and feed on fungi by drilling holes inside of it. In others, the larvae feed alongside adults by gnawing out shallow depressions on the fruiting bodies of fungi. The latter larvae are sluggish, heavily sclerotized, and somewhat flattened. The larval stage takes about 2 to 3 months from egg to pupation. It is not uncommon to see adults feeding along with larvae.
These beetles are generally active from dusk til dawn; adults of some tropical species of Megalodacne are regularly attracted to lights at night.
Taxonomy and systematics Megalodacne was first described by George Robert Crotch in 1873. The type species is Megalodacne fasciata. The genus Megalodacne is classified as type genus of subfamily Megalodacninae, along its presumed close allies Episcapha and Episcaphula; alternatively, it is the type genus of tribe Megalodacnini of an expanded subfamily Erotylinae.
Historically, several related genera – namely Episcapha, Episcaphula, Macrodacne, Mimodacne, Oretylus and Scaphodacne – were included in Megalodacne. An unusual problem complicating anatomical research of this genus and its closest relatives is their high body fat content. The fat exudes in museum specimens, making them slippery and the delicate parts of their anatomy (such as mouthparts and genitalia) very fragile, which results in the specimens becoming hard to handle without causing permanent damage to them.
Selected species Species of Megalodacne include:
Subgenus Megalodacne (Megalodacne) Crotch, 1876 - Nearctic and eastern Asia. Distinct seams on the sides of the prothorax extending to the forward margin. Megalodacne annulata (Megalodacne (Romodacne)?) Megalodacne bellula (Lewis, 1883) – Japan, Korea, & China Megalodacne chinensis (Crotch, 1876) – China Megalodacne congoana (Megalodacne (Romodacne)?) Megalodacne elongatula (Crotch, 1876) – Malacca, Java, Flores Megalodacne fasciata (Fabricius, 1777) – eastern North America Megalodacne heros (Say, 1823) – eastern North America Megalodacne immaculata (Chûjô and Kiuchi, 1963) – Japan Megalodacne marginata (Arrow, 1925) – Assam Megalodacne plagia Delkeskamp - Congo BasinDelkeskamp, Kurt (1953): Dacninæ (Coleoptera Clavicornia) Fam. Erotylidæ. In: de Witte, G.F.; Adam, W.; Janssens, A.; van Meel, L. & Verheyen, R.: Exploration du Parc National de l'Upemba (Mission G.F. de Witte) / Exploratie van het Nationaal Upemba Park (Zending G.F. de Witte) 17(4): 59-82. PDF fulltext (tentatively placed here) Megalodacne promensis (Arrow, 1925) – Burma, China Megalodacne savagei (Crotch) (Megalodacne (Romodacne)?) Megalodacne similima (Crotch, 1876) – Sarawak, Sumatra Megalodacne varia (Gorham, 1889) – Malaysia
Subgenus Megalodacne (Psephodacne) Heller, 1918 - Neotropics. Seams on prothorax sides vary from well-developed and long like in Megalodacne (Megalodacne), to indistinct and short, or entirely absent. Megalodacne audouini (Lacordaire, 1842) – MexicoAlvarenga, Moacyr (1994): Catálogo dos Erotylidae (Coleoptera) Neotropicais. [Catalogue of Neotropical Erotylidae (Coleoptera). Portuguese with English abstract.] Revista Brasileira de Zoologia 11(1): 1-175. . Megalodacne batesi Crotch, 1876 – Amazonian Brazil Megalodacne indica (Linnaeus, 1758) – Neotropics from Central America to Argentina (= M.multifida , M.quadriguttata) Megalodacne tortuosa (Lacordaire, 1842) – Mexico to Colombia?
Subgenus Megalodacne (Romodacne) Delkeskamp, 1937 - Tropical Africa and Madagascar. Formerly in Megalodacne (Psephodacne), but seams on the sides of the prothorax usually well-developed like in Megalodacne (Megalodacne). Megalodacne aspideoxesta Delkeskamp, 1937 - Cameroon to Congo Basin Megalodacne curvipes Fairmaire - Cameroon to Congo Basin Megalodacne dominula Bedel - Madagascar Megalodacne furcata Gorham - Togo to Congo Basin Megalodacne grandis (Fabricius, 1792) - Tanzania - widespread across tropical Africa Megalodacne natalensis (Fairmaire, 1891) - Congo Basin to Rift Valley region Megalodacne nesiotes Delkeskamp, 1937 - Madagascar Megalodacne sponsa Lacordaire - Madagascar
It is possible that undescribed Megalodacne species exist. A review of the UPN collection found 2 Megalodacne specimens – one each from Cundinamarca Department in central and Valle del Cauca Department in western Colombia – which did not seem to match the Megalodacne (Psephodacne) known from the region.Torres-Pachón, Mónica; Gasca-Álvarez; Héctor Jaime; Bustos-Martínez, Miller Felipe; Skelley, Paul E. & García-Sarmiento, Martha J. (2026): Erotylinae (Coleoptera: Erotylidae) de la colección entomológica del Museo de Historia Natural de la Universidad Pedagógica Nacional. ["Erotylinae (Coleoptera: Erotylidae) housed in Natural History Museum Entomological Collection of Universidad Pedagógica Nacional." Spanish with English abstract.] Revista UDCA Actualidad & Divulgación Científica 29(1): e3002.
Formerly placed here Moved to Amblyopus: Megalodacne bellopicta KuhntDelkeskamp, Kurt (1943): Aus Afrikas Erotyliden-Fauna (Col.) 9. Beitrag zur Kenntnis der Erotyliden. ["From the erotylid fauna of Africa. 9th contribution to the knowledge of erotylids." Article in German.] Dt. entomol. Z. 1943: 28-55. PDF fulltext.
Moved to Episcapha: Megalodacne asahinai Chûjô, 1938 (= M.yakushimensis) Megalodacne lewisi Nakane, 1950
Moved to Episcaphula: Megalodacne andamanensis (Gorham, 1888) (= M.affinis) Megalodacne eximia Arrow, 1922 Megalodacne laeta ArrowDelkeskamp, Kurt (1953): Dacninæ (Coleoptera Clavicornia) Fam. Erotylidæ. [Article in German.] In: de Witte, G.F.; Adam, W.; Janssens, A.; van Meel, L. & Verheyen, R.: Exploration du Parc National de l'Upemba (Mission G.F. de Witte) / Exploratie van het Nationaal Upemba Park (Zending G.F. de Witte) 17(4): 59-82. PDF fulltext Megalodacne megaloprepa Delkeskamp Megalodacne parva Delkeskamp, 1943 Megalodacne philippinarum (Lacordaire, 1842) Megalodacne tonkinensis (Heller, 1918 (1920)) (= M.major) Megalodacne transiens Delkeskamp, 1953 Megalodacne vitalisi Arrow, 1922
Moved to Macrodacne: Megalodacne fraudulenta (Heller, 1918 (1920)) Megalodacne luteoguttata Crotch, 1876 (= M.dohrni (Kuhnt, 1910) non Gorham, 1901)
Moved to Mimodacne: Megalodacne abnormalis Crotch, 1876 Megalodacne belgarum (Bedel, 1917) Megalodacne grandipennis (Fairmaire, 1891) Megalodacne imperatrix Gorham, 1883 Megalodacne kolbei Kuhnt, 1908 (sometimes in M.magnifica) Megalodacne longiuscula Fairmaire, 1891 Megalodacne magnifica Harold, 1878 Megalodacne rhodesiaca (Bedel, 1917)
Moved to Neodacne: Megalodacne okunii Chûjô, 1936
Moved to Oretylus: Megalodacne hislopi (Crotch, 1876) (= M.scabra)
References