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, but its exact delimitation has historically been much disputed and is still not entirely certain today.

 
Adult beetles of the genus Megalodacne range in size from 9 to, making them among the larger members of the family.

Distinguishing characteristics of the genus along with other members of the subfamily Megalodacninae include large eyes and a lack of depressions in the club joint of the antennae. The first three tarsomeres are also cylindrical and of similar shape and size, while the fourth is significantly shorter.

Species of the genus Megalodacne closely resemble members of the genera Episcapha and Episcaphula (some members of which were formerly classified under 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.

An example of which is the sap beetle (Nitidulidae) genus Glischrochilus. Their native ranges sometimes overlap as well, making it easy to confuse the two (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 2 to in length. Glischrochilus reaches a maximum length of only 12 mm. Megalodacne on the other hand are large beetles ranging from 9 to. 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.

Some tropical nocturnal species of Megalodacne are attracted to light.

Life cycle: 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.

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.

Selected species: Species of Megalodacne include:

Subgenus Megalodacne (Megalodacne) Crotch, 1876 - Nearctic and eastern Asia

• 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 promensis (Arrow, 1925) – Burma, China
• Megalodacne savagei (Megalodacne (Romodacne)?)
• Megalodacne similima (Crotch, 1876) – Sarawak, Sumatra
• Megalodacne varia (Gorham, 1889) – Malaysia

Subgenus Megalodacne (Mimodacne) Bedel, 1917 - Tropical Africa

• Megalodacne abnormalis Crotch, 1876
• Megalodacne belgarum Bedel, 1917
• Megalodacne grandipennis (Fairmaire, 1891) – Tanzania
• Megalodacne imperatrix Gorham, 1883 - Mozambique
• Megalodacne kolbei Kunt, 1908
• Megalodacne longiuscula Fairmaire, 1891
• Megalodacne magnifica Harold, 1878
• Megalodacne rhodesiaca Bedel, 1917 - Zimbabwe

Subgenus Megalodacne (Psephodacne) Heller, 1918 - Neotropics

• Megalodacne audouini (Lacordaire, 1842) – Mexico
• 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 (sometimes merged into Megalodacne (Psephodacne))

• Megalodacne curvipes
• Megalodacne furcata
• Megalodacne grandis (Fabricius, 1792) - Tanzania
• Megalodacne natalensis (Fairmaire, 1891)
• Megalodacne sponsa

Formerly placed here: 
Moved to Episcapha:

• Megalodacne asahinai Chujo, 1938 (= M.yakushimensis)
• Megalodacne lewisi Nakane, 1950

Moved to Episcaphula:

• Megalodacne andamanensis (Gorham, 1888) (= M.affinis)
• Megalodacne eximia Arrow, 1922
• Megalodacne philippinarum (Lacordaire, 1842)
• Megalodacne tonkinensis (Heller, 1918 (1920)) (= M.major)
• 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 Neodacne:

• Megalodacne okunii Chûjô, 1936

Moved to Oretylus:

• Megalodacne hislopi (Crotch, 1876) (= M.scabra)