Melolonthinae

Melolonthinae is a subfamily of the scarab beetles (family Scarabaeidae). It is a very diverse group; distributed over most of the world, it contains over 11,000 species in over 750 genera.[1] Some authors include the scarab subfamilies Euchirinae and Pachypodinae as tribes in the Melolonthinae.

Melolonthinae
Male Polyphylla alba (Melolonthini)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Scarabaeidae
Subfamily: Melolonthinae
Leach, 1819
Diversity
About 20–30 tribes
Synonyms

Hopliinae
Melolonthidae
Systellopodinae

Mating Rhizotrogus marginipes (Melolonthini), male on top – note sexually dimorphic antennae

Unlike some of their relatives, their habitus is usually not bizarre. They resemble the Rutelinae in being fairly plesiomorphic in outward appearance. Like in many Scarabaeidae, males have large fingered antennae, while those of the females are smaller and somewhat knobby. In the Melolonthinae, this sexual dimorphism is particularly pronounced. Many species have striking – though rarely brilliant or iridescent – hues and bold patterns of hairs.

Being often quite sizeable and swarming in numbers at certain times, for example the Amphimallon, Phyllophaga and Polyphylla "June beetles" or the Melolontha cockchafers – all from tribe Melolonthini – feature widely in folklore. Some Melolonthinae are economically significant pests. Other than the Melolonthini, the most diverse tribes are the Ablaberini, Liparetrini, Macrodactylini, Tanyproctini and Sericini.

Description

Melolonthinae adults range from 3 to 58 mm in length and are usually brown or black in colour. Some species are shiny, while many are covered in setae or scales. The clypeus, a structure on the head above the mouthparts, is not armed with teeth. There are two antennae, each with 7 to 10 segments, of which the last 3 to 7 segments are elongate and form a club, and the antennal bases are usually concealed from above. The scutellum is exposed at the base of the elytra. The margins of the elytra are straight instead of strongly curved. Each leg ends in a pair of tarsal claws that are often toothed or double.[2][3]

Larvae are C-shaped with a white/cream body and a darker, well-sclerotised head. They can be distinguished from other scarabaeid larvae by the galea and lacinia either partly fused proximally or fitting tightly together, the mandibles lacking stridulatory areas, the apical segment of the antenna about as wide as its penultimate segment, and the anal cleft usually Y-shaped or angulate.[3][4][5]

Life cycle

The Melolonthinae life cycle has the four stages of egg, larva, pupa and adult, similar to other beetles. Eggs are laid in soil, which is also where the larval and pupal stages occur. Adults occur above ground. The larval stage is long and may last up to two years, whereas the adult stage is short and lasts only a few days or weeks.[4]

Diet

Larval melolonthines feed on plant roots and humus. Known host plants include grasses, clover and sugarcane. Adults may (e.g. Automolius, Diphucephala, Heteronyx, Liparetrus, Phyllotocus and Sericesthis) or may not feed (e.g. Antitrogus and Rhopaea). Adults that feed do so on the leaves of trees, such as eucalypts, or on flowers or pollen.[4][5]

Behaviour

Adults are usually crepuscular or nocturnal, but the flower- and pollen-feeding species are often diurnal. They are often attracted to light.[4][5]

In feeding species, adults gather on trees and this helps them find each other to mate. In non-feeding species, virgin females emit a sex pheromone so that males can find them.[4]

Pests

Larvae of Sericesthis spp. are pasture pests, while larvae of Dermolepida albohirtum, Antitrogus and Lepidiota are sugarcane pests.[4] Lepidiota stigma is another sugarcane pest and also attacks corn, sorghum and various fruits.[3] Adults of Phyllophaga spp. can sometimes cause complete defoliation of deciduous trees.[5]

Systematics
Phyllotocus sp. (Sericini)
Stethaspis sp. (Colymbomorphini)

According to various authors, the living Melolonthinae are divided into about 20-30 tribes. Some notable genera and species are also listed here:

In addition, a prehistoric tribe, the Cretomelolonthini, is only known from fossils.

Several genera are of unclear relations; they are not yet firmly placed in a tribe:

  • Acoma
  • Conebius Fuavel, 1903
  • Costelytra – Liparetrini?
  • Hemictenius – Pachydemini?
  • Metascelis Westwood, 1842
  • Mycernus – Colymbomorphini?
  • Odontria – Liparetrini?
  • Prodontria – Liparetrini?
  • Psilodontria – Colymbomorphini?
  • Scythrodes – Liparetrini?
  • Sericospilus – Liparetrini?
  • Xenaclopus[6]

"Anonetus" and "Tryssus", both used by Erichson in 1847, are nomina nuda. Holophylla and Hoplorida are of uncertain validity.

References
  1. Cave, R.D. & Ratcliffe, B.C. (2008). Scarab beetles (Coleoptera: Scarabaeoidea). In J.F. Capinera (Ed.), Encyclopedia of Entomology (pp. 3273–3286. Heidelberg. Springer.
  2. "Subfamily Melolonthinae - May Beetles and Junebugs". bugguide.net. Retrieved 2023-01-18.
  3. "Melolonthinae". uk beetles. Retrieved 2023-01-18.
  4. "Australian Faunal Directory". biodiversity.org.au. Retrieved 2023-01-18.
  5. "Guide to New World Scarab Beetles-Scarabaeidae-Melolonthinae overview". unsm-ento.unl.edu. Retrieved 2023-01-18.
  6. Ocampo, F.C., Vaz-de-Mello, F.Z. (2008) The genus Xenaclopus Arrow (Coleoptera: Scarabaeidae): redescription and removal from the Aclopinae, with systematic notes. Zootaxa, 1916: 57–62.

Data related to Melolonthinae at Wikispecies Media related to Melolonthinae at Wikimedia Commons

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