Blister beetle

Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their toxicity to would-be predators.

Blister beetles
Hycleus lugens
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Polyphaga
Infraorder: Cucujiformia
Superfamily: Tenebrionoidea
Family: Meloidae
Gyllenhaal, 1810
Subfamilies

Eleticinae
Meloinae
Nemognathinae
Tetraonycinae

Description
Ivy bee (Colletes hederae), carrying parasitic triungulins of Stenoria analis

Blister beetles are hypermetamorphic, going through several larval stages, the first of which is typically a mobile triungulin. The larvae are insectivorous, mainly attacking bees, though a few feed on grasshopper eggs. While sometimes considered parasitoids, in general, the meloid larva apparently consumes the immature host along with its provisions, and can often survive on the provisions alone; thus it is not an obligatory parasitoid, but rather a facultative parasitoid, or simply a kleptoparasite. The adults sometimes feed on flowers and leaves of plants of such diverse families as the Amaranthaceae, Asteraceae, Fabaceae, and Solanaceae.

Cantharidin, a poisonous chemical that causes blistering of the skin, is secreted as a defensive agent. It is used medically to remove warts[1] and is collected for this purpose from species of the genera Mylabris and Lytta, especially Lytta vesicatoria, better known as "Spanish fly".

Toxicity

Cantharidin is the principal irritant in "Spanish fly", a folk medicine prepared from dried beetles in the family Meloidae.

The largest genus, Epicauta, contains many species toxic to horses. A few beetles consumed in a single feeding of alfalfa hay may be lethal.[2] In semiarid areas of the western United States, modern harvesting techniques may contribute to cantharidin content in harvested forage. The practice of hay conditioning, crushing the stalks to promote drying, also crushes any beetles present and causes the release of cantharidin into the fodder. Blister beetles are attracted to alfalfa and weeds during bloom. Reducing weeds and timing harvests before and after bloom are sound management practices. Using equipment without hay conditioners may reduce beetle mortality and allow them to escape before baling.[3]

Systematics

Subfamily Eleticinae

Tribe Derideini

  • Anthicoxenus
  • Deridea
  • Iselma
  • Iselmeletica

Tribe Morphozonitini

  • Ceriselma
  • Morphozonitis
  • Steniselma

Tribe Eleticini

  • Eletica

Tribe Spasticini

  • Eospasta
  • Protomeloe
  • Spastica
  • Xenospasta

Subfamily Meloinae
Black blister beetle, Epicauta pennsylvanica (Meloinae: Epicautini)
Cysteodemus armatus near Ridgecrest, California in the Mojave Desert: The white coating is cuticular wax, which can vary from white to yellow in this species .

Tribe Cerocomini

Tribe Epicautini

Tribe Eupomphini

Blister beetles like this Lytta vesicatoria (Meloinae: Lyttini) can be safely handled, provided the animal is not startled, and allowed to move around freely. Otherwise, painful poisonings may occur.
Meloe violaceus (Meloinae: Meloini): Note the drop of dark orange defensive fluid on its thorax.
Mylabris quadripunctata (Meloinae: Mylabrini)

Tribe Lyttini

  • Acrolytta
  • Afrolytta
  • Alosimus
  • Berberomeloe
  • Cabalia
  • Dictyolytta
  • Eolydus
  • Epispasta
  • Lagorina
  • Lydomorphus
  • Lydulus
  • Lydus
  • Lytta
  • Lyttolydulus
  • Lyttonyx
  • Megalytta
  • Muzimes
  • Oenas
  • Parameloe
  • Paroenas
  • Physomeloe
  • Prionotolytta
  • Prolytta
  • Pseudosybaris
  • Sybaris
  • Teratolytta
  • Tetraolytta
  • Trichomeloe

Tribe Meloini

Tribe Mylabrini

A yellow-and-black species of Actenodia, one of many known in South Africa as "CMR beetle"
  • Ceroctis
  • Croscherichia
  • Hycleus
  • Lydoceras
  • Mimesthes
  • Mylabris
  • Paractenodia
  • Pseudabris
  • Semenovilia
  • Xanthabris

Tribe Pyrotini

  • Bokermannia
  • Brasiliota
  • Denierota
  • Glaphyrolytta
  • Lyttamorpha
  • Picnoseus
  • Pseudopyrota
  • Pyrota
  • Wagneronota

Genera incertae sedis

  • Australytta
  • Calydus
  • Gynapteryx
  • Oreomeloe
  • Pseudomeloe

Subfamily Nemognathinae
Horia sp. from Bannerghatta (Bangalore)
Sitaris muralis (Nemognathinae: Sitarini)

Tribe Horiini

Tribe Nemognathini

Tribe Sitarini

  • Allendeselazaria
  • Apalus
  • Ctenopus
  • Glasunovia
  • Nyadatus
  • Sitaris
  • Sitarobrachys
  • Stenoria

Genera incertae sedis

Subfamily Tetraonycinae

Tribe Tetraonycini

See also

References
  1. Bhattacharjee, Pradip; Brodell, Robert T. (2003). "Cantharidin". In Robert T. Brodell; Sandra Marchese Johnson (eds.). Warts: Diagnosis and Management—an Evidence-Based Approach. London: Martin Dunitz. pp. 151–160. ISBN 1-84184-240-0.
  2. University of Arizona VDL Blister Beetle Poisoning in Horses Archived July 24, 2008, at the Wayback Machine
  3. University of Colorado Extension Blister Beetles in Forage Crops Archived 2015-01-10 at the Wayback Machine
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