Spanish Fly

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Spanish Fly: The Beetle. History, Facts and More
Spanish Fly
  1. Commonly found throughout southern Europe, parts of Central Asia and Siberia, the Spanish Fly (Lytta vesicatoria) is actually a beetle. They are signified by the secretion of Cantharidin, which is common among almost all male species of the blister beetle family (Meloidae).
  1. The Spanish Fly, and some of its related species, were earlier used for the preparation of medicines by conventional apothecaries. Cantharidin, a toxic, defensive chemical found in the blister beetle, had been used for over a thousand years as a sexual stimulant. In concentrated amounts, the chemical causes severe blistering. It is potent enough to cause serious complications and is fatal above a certain dosage.


Spanish Fly Insect

The Spanish Fly has a bright metallic, emerald-green body, which often appears as golden-green due to the phenomenon known as iridescence. In simple terms, iridescence is the property due to which the color of some surfaces appear to change gradually and is often found to naturally occur. Examples include butterfly wings and feathers of certain birds.

It has a soft body and usually grows up to 20 mm (0.79 inches) in length and 5 mm (0.20 inches) in width. Its scientific name is derived from Greek, with lytta meaning marital rage, insanity, Bacchic frenzy (refer to the Maenads - the mad, female followers of Dionysus, the Greek god of wine and fertility. Dionysus was known as Bacchus in Roman mythology) or rabies. The vesica is Latin for blisters.

Scientific Classification of the Spanish Fly

The Spanish Fly (lytta vesicatoria) belongs to the order Coleoptera (beetle) and the Meloidae (blister beetle) family. Coleoptera, or the order of the beetles, is the largest of all the orders, with over 400,000 species. They are found throughout the globe, except for the polar regions and the sea. They are an integral part of the ecosystem, responsible for breaking down animal and plant debris, feeding on plants, fungi and, at times, smaller invertebrates.

There are about 7,500 known species of blister beetles known globally. It is also one of among at least 330 species that have been described in the Meloinae sub-family. The tribe is known as Lyttini. The Spanish Fly is associated with the genus Lytta, available worldwide but majorly concentrated in North America. On a worldwide scale, there are over 100 species belonging to the genus Lytta, of which 70 are common in the northern part of America.

Availability and Eating Habits

Lytta Vesicatoria - Spanish Fly

While the Spanish Fly is mainly a south European insect, it is found throughout a wide region of Europe. It is also found eastward in Central Asia and the cold Siberian region. The beetle has been reported in various parts of North and South Asia, excluding China. There have been sightings of the Spanish Fly in the southern part of Great Britain and Poland, also.

The adult beetles are primarily vegetarian, feeding mainly on leaves. They have been known to feed on various small plants, including ash, lilac, honeysuckle, plum and rose. They also feed on the leaves of amur privet, elm and the white willow tree.


Cantharidin secretion is exclusive among the male species of the Spanish Fly beetles. It is present in the spermatophore (capsule or globule containing spermatozoa used for reproduction by the males of salamanders and certain insects). The spermatozoa are then transferred to the females during mating, transferring the cantharidin as a nuptial gift. The transfer act also increases the reproductive ability of the male. The average life expectancy of a single beetle is about 1 year.

A female blister beetle lays about 3000 to 4000 eggs, of which a few survive to fully grow into adults. The females lay their eggs in the ground near the nests of solitary bees. The hatched larvae climb to the flowers through the stems of a flowering plant and wait for the arrival of the female bee.

Using the claws on their legs, the larvae (named triungulins- from Latin tri - three; ungulus - claw) latch themselves on to the bee, be it male or female. In the case of a male bee, the larvae wait for the bee to mate and then attach themselves to the female bee. After being taken back to the hives, the triungulins feed on bee larvae and bee food supplies, positioning themselves between predators and parasites. There are quite a few stages within the entire insets; in a process called hypermetamorphosis, the fully grown beetles emerge from the bees’ nest and fly to a nearby food source of a plant.


Cantharidin is an organic compound belonging to the terpenoid class. It is a colorless and odorless fatty substance. It's also a burn agent secreted from the legs of the male Spanish Fly beetle - it causes severe blisters and is poisonous in large doses.

It has been reported that Cantharidin is a necessary ingredient, functioning like an aphrodisiac for the courting and mating rituals of Spanish Fly and other beetles. The vesicant chemical is initially procured by the male beetles from an exogenous source - mostly by ingestion. After ingestion, the Cantharidin secretion begins in the cephalic gland, which is present exclusively in the head of the males.

During their courting rituals, the males present the females with Cantharidin (in the form of an “oozing gift”). The females of the species become allured, and during the process of mating, the males transfer the majority of the secreted Cantharidin along with spermatozoa. The female beetles use Cantharidin to cover the eggs for defense against predators. The synthesis of Cantharidin can be checked by 6-fluoro mevalonate. The primary cause of the inhibition is usually attributed to the fluorine substituent.

The poisoning due to Cantharidin is a cause for concern among many animals, especially horses. Beetles feed on leaves and at times move to crop fields that grow livestock (alfalfa). Horses are known to be very sensitive against the blistering chemical secreted by Spanish Fly beetles within the median lethal dose (LD50), roughly around 1mg/kg of the horse’s body weight. The Great Bustard - a large, flightless bird found in Morocco, Europe and East Asia - is known to become intoxicated due to Cantharidin poisoning from ingesting blister beetles.

According to research, Cantharidine causes the release of serine proteases, the enzymes responsible for the breakdown of peptide bonds in proteins. Once absorbed through the lipid membranes by the epidermal cells, Cantharidin triggers a chain of reactions that ultimately leads to acantholysis (loss of cellular adhesion and connections) and blistering of the skin.

There are no scars left after the lesions heal. It has been known to be beneficial against cutaneous leishmaniasis, a disease caused by single-celled parasites transmitted by the bite of a phlebotomine sandfly. Laboratory studies and reports also suggest that Cantharidin may be beneficial in fighting cancer cells. The positive feedback may be due to PP2A inhibition. It can also be used to cure water warts (molluscum contagiosum) and other related infections if used in correct diluted dosages.

Use as an Aphrodisiac/Sexual Stimulant- Science or Myth?

Several aphrodisiacs claim to contain Cantharidin from blister beetles. It is supposed to rapidly arouse sensual and erotic feelings among both males and females. However, the reality is that most products are fake and contain water.

There is a line to be drawn between history and folklore. In the case of the Spanish Fly, it is more or less the latter. It was said to have been used in ancient Roman orgies. A Roman empress was said to use Cantharidin to encourage illicit sexual liaisons among the powerful members of Roman society in order to find information to blackmail them. It was also said to be used by ancient Greek kings, queens and mistresses to spice up their physical encounters.

The preparations, made with crushed dried beetles and mixed with drinks or sweets, caused the genitals to swell. It also generated a feeling of warmth throughout the entire body. However, it is important to note that these feelings of warmth were due to inflammation and not arousal.

Cantharidin Poisoning

The vesicant properties of Cantharidin are not the only things that make it dangerous to humans and other animals. It is a highly potent toxin, able to cause diseases and toxins if ingested or consumed in concentrated doses. Some of the symptoms synonymous with Cantharidin poisoning include severe mouth-burns, dysphagia (difficulty swallowing), nausea, hematemesis (vomiting blood) and gross hematuria (blood in urine). It may also cause extreme painful urination and rectal bleeding.

Damages to the gastrointestinal tract include blisters and mucosal erosion, and hemorrhage through the wall linings have been noted in some cases, along with seizures and cardiac abnormalities. The median lethal dose in the case of humans is 0.5 mg/kg of body weight. A dosage of 10 mg can prove to be fatal. In rare instances, prolonged erections or priapism have also been reported.

Strictly forbidden in the USA, the traditional use of Cantharidin as an aphrodisiac is one of the primary reasons for involuntary Cantharidin poisoning.

Notable Cases of Cantharidin Poisoning

According to a recent report from Zimbabwe, a 4-year old girl was reported to have swallowed a mylabris dicincta (a variant of blister beetle). Her diagnosis began after she began to show the traditional symptoms of Cantharidin poisoning - hematuria and severe pain throughout the abdominal cavity. After proper treatment and supervision at the medical center, she recovered and was discharged after a period of 9 days.

The South American liberator Simon Bolivar was poisoned with the administration of Spanish Fly.

Infamous French playwright Marquis de Sade was the cause of the death of several prostitutes in 1772. The cause of the death of the prostitutes was said to be sweet aniseed laced with the Spanish Fly.

Culinary and Other Uses

The Spanish Fly was consumed as a food item in parts of North African countries, especially Morocco. The sale of the spice blend consisting of green beetles - the "ras el hanout" - was banned in the 1990s. The beetles were occasionally used along with a mixture of spices, sugar, hashish, dry fruit pastes and the peels of certain fruits, to make the African jam-spread Dawamesk. Blister beetles, along with the herb wolfsbane (Aconitum) and human excrement were the key ingredients in the world’s first stink bomb made in ancient China.

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