Blister beetle

thumb|At [[Mumbai]]

Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 2,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their toxicity to would-be predators.

Description

thumb|right|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.

thumb|center|thumbtime=31|Female [[Epicauta funebris|margined blister beetle pursued by multiple males]]

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

Toxicity

Cantharidin from blister beetles has been used to create primarily aphrodisiacs but also poisons throughout history.

The largest genus, Epicauta, contains many species toxic to horses. A few beetles consumed in a single feeding of alfalfa hay may be lethal. 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.

Evolutionary history

The family is thought to have begun diversifying during the Early Cretaceous. The oldest fossil of the group is a larva (triangulin) found phoretic on a schizopterid bug from the mid Cretaceous Burmese amber, dated to around 99 million years ago.

Biology

Blister beetles are known to attract bees with sex pheromones, then hitch a ride to their nests to dine on the bees' eggs. Ryan Alam of the Max Planck Institute for Chemical Ecology and colleagues analyzed the larvae of the European black oil beetle (Meloe proscarabaeus) --- they found a mix of molecules called monoterpenoids, rare in insects but common in flowers.

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

thumb|right|Black blister beetle, [[Epicauta pennsylvanica (Meloinae: Epicautini)]]

thumb|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 [http://bugguide.net/node/view/38586].]]

Tribe Cerocomini

Anisarthrocera
Cerocoma
Diaphorocera
Rhampholyssa
Rhampholyssodes

Tribe Epicautini

Denierella
Epicauta
Linsleya
Psalydolytta

Tribe Eupomphini

Cordylospasta
Cysteodemus
Eupompha
Megetra
Phodaga
Pleropasta
Tegrodera

thumb|right|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.]]

thumb|right|[[Meloe violaceus (Meloinae: Meloini): Note the drop of dark orange defensive fluid on its thorax.]]

thumb|right|[[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

Cyaneolytta
Lyttomeloe
Meloe
Spastomeloe
Spastonyx

Tribe Mylabrini

Actenodia

thumb|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

thumb|right|[[Horia (beetle)|Horia sp. from Bannerghatta (Bangalore)]]

thumb|right|[[Sitaris muralis (Nemognathinae: Sitarini)]]

Tribe Horiini

Cissites
Horia
Synhoria

Tribe Nemognathini

Cochliophorus
Euzonitis
Gnathium
Gnathonemula
Leptopalpus
Megatrachelus
Nemognatha
Palaestra
Palaestrida
Pseudozonitis
Rhyphonemognatha
Stenodera
Zonitis
Zonitodema
Zonitolytta
Zonitomorpha
Zonitoschema

Tribe Sitarini

Allendeselazaria
Apalus
Ctenopus
Glasunovia
Nyadatus
Sitaris
Sitarobrachys
Stenoria