The Spanish fly is an emerald-green beetle in the family Meloidae, Lytta vesicatoria. Other species of blister beetle used by apothecaries are often called by the same name. Lytta vesicatoria is sometimes incorrectly called Cantharis vesicatoria, but the genus Cantharis is in an unrelated family, Cantharidae.
Cantharidin (etymology: Greek kantharis, beetle) is a powerful irritant vesicant (blister-inducing) substance obtained from many blister beetles, and sometimes given the nickname "Spanish fly." Cantharidin is claimed to have aphrodisiac properties, as a result of its irritant effects upon the body's genitourinary tract, and can result in poisoning if ingested. Ingestion of blister beetles from infested hay causes similar serious toxic symptoms in animals.
The beetle 
Lytta vesicatoria is 15 millimetres (0.59 in) to 22 millimetres (0.87 in) long and 5 millimetres (0.20 in) to 8 millimetres (0.31 in) wide. Adult beetles feed on leaves of ash, lilac, amur privet and white willow trees; larvae are parasitic on the brood of ground nesting bees. The beetle lives in scrublands and woods throughout southern Europe and eastward to Central Asia and Siberia.
Cantharidin, the principal irritant in Spanish fly, was first isolated and named in 1810 by Pierre Robiquet, a French chemist then living in Paris, from Lytta vesicatoria. Robiquet demonstrated that cantharidin was the actual principle responsible for the aggressively blistering properties of the coating of the eggs of that insect, and established that cantharidin had very definite toxic and poisonous properties comparable in degree to that of the most violent poisons known in the 19th century, such as strychnine.
Cantharidin, a terpenoid, is produced by various insect species. The body of the beetle contains up to 5% cantharidin. The crushed powder is of yellowish brown to brown-olive color with iridescent reflections, of disagreeable scent and bitter flavor.
Early uses 
Medical use dates back to descriptions from Hippocrates. Plasters made from wings of these beetles have been used to raise blisters. In ancient China, the beetles were mixed with human excrement, arsenic and wolfsbane to make the world's first recorded stink bomb.
Various preparations of desiccated Spanish flies have been used as some of the world's oldest alleged aphrodisiacs, with a reputation dating back to the early western Mediterranean classical civilizations:
- In Roman times, Livia, the scheming wife of Augustus Caesar, slipped it into food hoping to inspire her guests to some indiscretion with which she could later blackmail them.
- Henry IV (1050–1106) is known to have consumed Spanish fly at the risk of his health.
- In 1572, Ambroise Paré wrote an account of a man suffering from "the most frightful satyriasis" after taking a potion composed of nettles and cantharides.
- In the 1670s, Spanish fly was mixed with dried moles and bat's blood for a love charm made by the magician La Voisin.
- It was slipped into the food of Louis XIV to secure the king's lust for Madame de Montespan.
- In the 18th century, cantharides became fashionable, known as pastilles Richelieu in France.
- The Marquis de Sade is claimed to have given aniseed-flavored pastilles that were laced with Spanish fly to prostitutes at an orgy in 1772. He was sentenced to death for poisoning and sodomy, but later reprieved on appeal.
Miscellaneous uses 
Spanish fly is used by many people as an aphrodisiac, although it is now produced in the laboratory under safe, strict conditions and without the use of cantharadin the poisonous and lethal toxic used in old remedies from many years ago. Although spanish fly can irritate the genitals resulting in increased blood flow that can mimic the engorgement that occurs with sexual excitement, symptoms of cantharidin poisoning include burning of the mouth, dysphagia, nausea, hematemesis, gross hematuria, and dysuria. 
In powder, mixed with the food, cantharide could go unnoticed. Aqua toffana, or aquetta di Napoli, was one of the poisons associated with the Medicis. Thought to be a mixture of arsenic and cantharides, it was reportedly created by an Italian countess, Toffana. Four to six drops of this poison in water or wine was enough to deliver death in a few hours.
In order to determine if a death had taken place by the effects of Spanish fly, investigators resorted to the vesicación test. One of those test methods consisted of rubbing part of the internal organs of the deceased, dissolved in oil, on the shaved skin of a rabbit; the absorption of the cantharides and its blistering effect are such that they became visible on the skin of the rabbit.
Commercial products 
Culinary use 
Dawamesk, a spread or jam made in North Africa and containing hashish, almond paste, pistachio nuts, sugar, orange or tamarind peel, cloves and other various spices, occasionally included cantharides.
In Morocco and other parts of North Africa, a spice blend called Ras el hanout included cantharides in its list of ingredients at one time. However, the sale of cantharides in Moroccan spice markets was banned in the 1990s.
- From Greek lytta, rage and Latin vesica, blister.
- Richardg B. Selander (1991). On the Nomenclature and Classification of Meloidae (Coleoptera). Insecta Mundi 5 (2): 65–94.
- Karras, David J.; Farrell, SE; Harrigan, RA; Henretig, FM; Gealt, L (1996). "Poisoning from "Spanish fly" (cantharidin)". The American Journal of Emergency Medicine 14 (5): 478–83. doi:10.1016/S0735-6757(96)90158-8. PMID 8765116. "While most commonly available preparations of Spanish fly contain cantharidin in negligible amounts, if at all, the chemical is available illicitly in concentrations capable of causing severe toxicity. Symptoms of cantharidin poisoning include burning of the mouth, dysphagia, nausea, hematemesis, gross hematuria, and dysuria. Mucosal erosion and hemorrhage is seen in the upper gastrointestinal (GI) tract. Renal dysfunction is common and related to acute tubular necrosis and glomerular destruction."
- The Merck Veterinary Manual. 2010. Retrieved 22 August 2011. "The severity of clinical signs associated with cantharidin toxicosis vary according to dose. Signs may range from mild depression or discomfort to severe pain, shock, and death."
- "Spanish fly." Grzimek's Animal Life Encyclopedia. The Gale Group, Inc, 2005. Answers.com 22 Nov. 2009.
- Expériences sur les cantharides, Robiquet. M., Annales de Chimie, 1810, vol. 76, pp. 302–322.
- (Theroux 1989, p. 54)
- James, Peter (1995). Ancient Inventions. Ballantine Books. p. 177. ISBN 0-345-40102-6.
- (Milsten 2000, p. 170)
- (Cavendish 1968, p. 333)
- Ford, Peter; Howell, Michael (1985). The beetle of Aphrodite and other medical mysteries. New York: Random House. ISBN 0-394-54797-7.
- (Gonzalez-Wippler 2002, p. 221)
- AJ Giannini, HR Black. The Psychiatric, Psychogenic and Somatopsychic Disorders Handbook. Garden City, New York. Medical Examination Publishing Co., 1978. p. 97. ISBN 0-87488-596-5.
- (Stevens 1990, p. 6)
- Moen, L.; Shwayder, T., Chang M. (October 2001). "Cantharidin revisited: a blistering defense of an ancient medicine". Archives of Dermatology (137): 1357–1360.
- (Davidson 1999)
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