BLISTER BEETLE INTOXICATION

 

CANTHARIDIN POISONING

 

(http://www.ent.iastate.edu/imagegal/coleoptera/blister/0121.35margblistb.html)

 

Chem 377: Chemistry of Drugs and Poisons

Spring 2000

Meredith May

 

HISTORY OF CANTHARIDIN:

 

Blister beetles produce cantharidin, which is toxic to people and animals. For centuries, cantharidin was prescribed as a cure for a variety of ailments.

 

Spanishfly or cantharis, a preparation of dried meloid beetles, was thought to cure gout, carbuncles, rheumatism and many other medical disorders.

 

The barbarisms practiced upon the American people during the nineteenth century by the application of cantharis beetles for all sorts of ailments, in addition to treating the misery endured by those who suffered in the Revolutionary War (Metcalf, 1962).

 

The dried and crushed body of the beetle was used medically as an irritant and diuretic, but was also regarded as a potent aphrodisiac, especially for older gentlemen before its dangerous nature was recognized. Today, the toxic properties of cantharidin are more widely recognized and its use is largely restricted to veterinarians, who employ it as a counterirritant and blistering agent. (Davidson, 1987).

 

The earliest descriptions of the use of cantharidin as a medicine dates back to antiquity. Such people as Hippocrates, Celsus and Pliny mention the drug. The Roman empress Livia (58 B.C.-A.D. 29) slipped it into the food of other members of the imperial family to stimulate them into committing sexual indiscretions that could later be used against them (Metcalf, 1962).

  

STRUCTURE OF CANTHARIDIN:

 

Figure 1: Structure of the toxin

(http://www.chemfinder.com/result.asp)

C₁₀H₁₂O₄, Molecular Weight: 196.2024

Melting Point = 218 °C

 

SYNONYMS:

 

• (3aalpha, 4beta, 7 beta, 7aalpha)-hexahydro-3a, 7a-dimethyl-4,7-epoxyisobenzofuran-1,3-dione
• Exo-1,2-cis-dimethyl-3,6-epoxyhexahydrophthalic anhydride
• Cantharides
• Cantharone
• Spanish fly

 

SOURCE OF TOXIN:

 

Blister beetles are classified in the family Meloidae, order Coleoptera that range from the southwestern U.S. to the East Coast (http://agweb.okstate.edu/pearl/plantsoil/crops/f-2072.pdf). This family includes over 300 species in the United States and more than 2,500 worldwide. The genus Epicauta is the largest and contains many species that concern forage producers in semi-arid regions of the western United States.

 

The striped blister beetles are classified as Epicuata vittata, E. temexa and E. occidentalis, the black blister beetles are E. pennsylvanica and E. conferta, the spotted blister beetle is E. paradalis, and the Spanishfly (relative of the American blister beetle from Europe) is Lytta vesicatoria (http://encarta.msn.com). These beetles can be seen in figure 2.

 

These beetles carry a venomous substance diffused throughout their body, especially in their blood, rather than confined to particular glands. Blister beetles produce this substance called cantharidin; a potent chemical that possesses caustic or blistering properties when the insects are accidentally crushed or handled roughly. They are also poisonous if taken internally, as when livestock eat them while grazing (Aiello, 1998).

 

Figure 2: Various types of blister beetles

(http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/blister.htm)

  

TOXIC PRINCIPLE:

 

Cantharidin is an odorless, colorless compound that is soluble in various organic solvents, but only slightly soluble in water (Davidson, 1987). Cantharidin shown in figure 1 is a bicyclic terpenoid. This toxin is rapidly absorbed from the gastrointestinal tract and excreted in the urine. Cantharidin is the poisonous substance in blister beetles and is thought to protect the beetles from predation. It is comparable to cyanide and strychnine in toxicity (Aiello, 1998). The toxin is found in the hemolymph and gonads of the blister beetle. The content of cantharidin in the beetles ranges from 1-5% of dry weight (Carrel, 1993).

 

CANTHARIDIN PRODUCTION IN A BLISTER BEETLE:

 

Cantharidin is present in all ten-life stages of the complex metamorphosis shown in figure 5 of the blister beetle (Carrel, 1993). The first five larval stages accumulate cantharidin as they feed and grow in size. When disturbed, they exude cantharidin in a milky oral fluid, not in hemolymph which adult beetles reflexively discharge from leg joints. Two subsequent larval stages and the pupa do not feed, grow, regurgitate or change in their defensive reserves (110-mg catharidin/insect, regardless of sex) (Carrel, 1993). Adult beetles kept in isolation for 60-90 days exhibit a pronounced sexual dimorphism in cantharidin production. Cantharidin is produced only by male blister beetles and is stored until mating. The male beetle biosynthesizes about 17 mg of the toxin, representing 10% of his live weight (Carrel, 1993). Male beetles have the highest levels of the toxin and transfer cantharidin to the females during copulation.

 

BLISTER BEETLES:

 

Blister beetles are large, approximately 0.5-1.0 inch long, and can be of various colors (Metcalf, 1962). Their colors are beautiful; metallic green, blue, coppery or rose, spotted or striped yellow and black, while some are unmarked gray, brown or black. As shown in figure 3, these beetles have long, soft cylindrical bodies with a narrow prothorax forming a pronounced neck area that makes them easy to distinguish from other beetles.

 

Figure 3:

(http://www.ars-grin.gov/ars/MidWest/Ames/pests/blister.html)

 

Blister beetles are gregarious and often congregate in large swarms within alfalfa fields as seen in figure 4. These beetles do not migrate long distances. In alfalfa, they are often found within 50 yards of the field margin (Minks, 1988). The adults are foliage feeders that are quite destructive attacking many flowering plants, field and garden crops, clover, alfalfa, soybeans and weeds.

 

Figure 4: A typical swarm of striped blister beetles in alfalfa hay

(http://clay.agr.okstate.edu/alfalfa/images/insects/clusblsb.htm)

 

Adult beetles mate and the females deposit fifty to several hundred eggs in the soil crevices during the summer. At hatching in 12 days, the active larvae are predators feeding on grasshopper and cricket eggs in order to reach maturity (Minks, 1988). The larvae are an important biological control agent for grasshoppers. During the next 25 to 28 days the larva molts four times, undergoing a remarkable series of changes in form and appearance known as hypermetamorphosis in figure 5 during which its legs, mouth parts, and other appendages grow progressively smaller (Davidson, 1987). The beetles emerge as adults in late spring and summer living for 4 to 6 weeks (Minks, 1988). The seasonal and peak occurrence of the different types of blister beetles in alfalfa varies (http://www.oznet.ksu.edu/library/entml2/mf959.pdf). They are very restless, active beetles that tend to feed together in swarms. Adults fly into fields, where they feed on foliage. Blister beetles are often worse in fields adjacent to weedy grassy areas that contain an abundance of grasshopper eggs.

 

Figure 5: The ten life stages of the blister beetle

(http://ipmwww.ncsu.edu/AG295/html/blister_beetles.htm)

 

 

MODE OF ACTION:

 

The Latin name of the beetle derives from the Greek word lytta, meaning rage and the Latin word vesica meaning blister (Carrel, 1993). This points to the main effects of poisonous doses resulting in internally mental illness and externally a vesicant action. It is highly irritating and causes acantholysis and vesicle formation when in contact with the skin or mucous membranes.

 

Cantharidin is a vesicant and a mucousal irritant which may cause oral and urinary bladder ulcers. After ingestion, it is absorbed from the GI tract and is rapidly excreted by the kidneys. Cantharidin inhibits phosphatase 2A which is involved in the control of cell proliferation, activity of membrane-associated channels and receptors, modulation of protein kinases and phosphatases (Eldridge, 1995).

 

ENVIRONMENTAL CONDITIONS SURROUNDING TOXICITY:

 

Blister beetles containing the toxin cantharidin can be incorporated with alfalfa during forage conservation. Blister beetle contaminated hay is almost always the result of beetles being crushed prior to baling. Beetles are killed by the crimper rollers and trapped in the hay. Remains of blister beetles may be concentrated in a small portion of the hay from a field. Beetles are also killed and trapped when forage is driven on before the beetles have had time to escape. If left alone, the vast majority of beetles leave alfalfa shortly after cutting.

 

Cantharidin inadvertently ingested with animal feed may cause illness or death in livestock. Even if the beetles are killed, the problem still exists. Cantharidin is a very stable compound that remains toxic in dead beetles. (Aiello, 1998). It was reported that blister beetles trapped in alfalfa hay were fed to valuable racehorses in Florida. Even though the beetles were dead the horses died of cantharidin poisoning (Guglick, 1996).

 

 

 

TOXICITY:

 

Cantharidin is highly toxic by ingestion, but can also be taken up through the skin and mucous membranes. The poisoning is called cantharidism and can consist of severe gastrointestinal disturbances and nephritis. Collapse occurs in several cases and death might follow.

 

A consumption of 1.6g of pulverized beetles containing the toxin led to death after 26 hours. Ten mg of pure cantharidin resulted in a fatality, whereas poisoning by 1.3mg did not (Davidson, 1987). Cantharidin is excreted by the kidney and will during excretion irritate the entire urinary tract. The irritation of the urethra will increase the blood flow to this region and might result in priapism, a persistent abnormal erection of the penis (Metcalf, 1962). It is likely that the priapism is the origin of the use of Spanish fly as an aphrodisiac.

 

Cantharidin is the sole toxin, but its concentration in beetles varies widely. Blister beetle intoxication and fatality is most commonly seen in equine, but comparable doses can poison cattle or sheep (Guglick, 1996). With such a variation in cantharidin content of beetles within the same species, it is difficult to determine the number of beetles to make a lethal dose. The cause of this variation is unknown, but partially relates to sex of the beetles, time of year and food source. The high variability in cantharidin content partially explains the wide range of beetles reported to cause death in horses. A single beetle or as many as 150 to 200 beetles have been reported as a lethal dose (Aiello, 1998). The minimal lethal oral dose in equids appears to be less than 1 mg/kg body weight (Guglick, 1996). The estimated number of beetles for a lethal dose of cantharidin vary depending on the type of blister beetle as well as the size of the horse that was infected (http://clay.agr.okstate.edu/alfalfa/webnews/blister.htm). The toxicity of cantharidin does not decrease in stored hay, and cantharidin is also toxic to people, dogs, cats, rabbits and rats.

 

CLINICAL SIGNS:

 

Clinical signs are related to the amount of cantharidin ingested. The onset and duration of signs can vary from hours to days. Cantharidin can cause severe skin inflammation and blisters. The toxin is absorbed through the intestine and can cause symptoms ranging from mild depression or discomfort to severe pain, gastroenteritis, nephritis, shock and death. Massive doses of cantharidin cause shock and death within 6 hours (Helman, 1997). Smaller doses cause the following symptoms: colic, anorexia, depression, sweating, ulceration of oral mucosa, washing muzzle in water, soft stools, dysuria, elevated body temperature, increased respiration and heart rates, muscular rigidity, short-strided gait, collapse, dehydration and synchronous diaphragmatic flutter (SDF) due to hypocalcemia (Aiello, 1998).

 

There is frequent urination during the first 24 hours after ingestion, accompanied by inflammation of the urinary tract. This irritation may also result in secondary infection and bleeding. In addition calcium and magnesium levels in horses drastically lower and heart muscle tissues are destroyed. Typical signs are related to GI and urinary tract infection, endotoxemia and shock, hypocalcemia and myocardial dysfunction.

 

PATHOLOGY:

 

Acantholysis of the gastrointestinal tract (esophagus and nonglandular portion of stomach) as well as the urinary bladder is present. Gastritis and enterocolitis is evident characterized by mucosal hyperemia, hemorrhage, ulceration, edema and excessive fluid and edema (Aiello, 1998). Hemorrhagic and ulcerative cystitis along with vesication of the nonglandular portion of the stomach results.

 

DIAGNOSIS:

 

Cantharidin poisoning can be identified through observed clinical signs along with gross and microscopic pathologic signs. Whether the horse has consumed alfalfa hay in the past may also help with the diagnosis to know if the horse was possibly exposed to blister beetles. Chemical analysis can also be performed for cantharidin. These methods include high-pressure liquid chromatography (HPLC) and gas chromatography of samples from the gastrointestinal content, urine and serum (Ray, 1989). Improved methods involve partial purification of urine and gastric content extracts, using silica cartridges, followed by analysis using gas chromatography and mass spectrometry. The concentration of cantharidin in urine becomes negligible in 3-4 days (Ray, 1980). Therefore urine should be collected early in the course of disease if it is to be analyzed for cantharidin content.

 

 

 

TREATMENT:

 

There exists no specific antidote for cantharidin poisoning. Management of blister beetles is difficult. Treatment thresholds have not been established and chemical controls often do not eliminate the problem because dead beetles can be picked up in the hay and more beetles can migrate into the field. The main focus should be centered on cantharidin removal, reduction of absorption and immediate symptomatic therapy.

 

The removal of cantharidin can be accomplished by removing alfalfa or suspected feed from the animals. Several insecticides are registered for blister beetle control such as Sevin and Methoxychlor (Aiello, 1998). Strip-spraying field edges may be the best approach when blister beetles are observed in adjacent areas. Reduction of the toxin can be accomplished through administration of activated charcoal and mineral oil. Symptomatic therapy includes administration of fluids to correct dehydration and promote diuresis, analgesics, calcium and magnesium replacement, and broad-spectrum antibiotics (Minks, 1988).

 

(http://clay.agr.okstate.edu/alfalfa/images/insects/blsbt-05.htm)

 

REFERENCES:

 

Aiello, Susan E. Cantharidin Poisoning. The Merck Veterinary Manual. 8^th Ed. Merck & Company, Inc., 1998. pp. 2028-9.

Carrel, J. E., M. H. McCairel and A. J. Slagle. Cantharidin production in a blister beetle. Experientia. 49: 171-4, 1993.

Davidson, Ralph H. and William F. Lyon. Insect Pests of Farm, Garden and Orchard. New York: John Wiley & Sons, Inc., 1987.

Eldridge, R. and J. E. Casida. Cantharidin effects on protein phosphatases and the Phosphorylation state of phosphoproteins in mice. Toxicol Appl Pharmacol. 130: 95-100, 1995.

Guglick, M. A., C. G. MacAllister and R. Panciera. Equine Catharidiasis. Compend Contin Educ Pract Vet. 18: 77-83, 1996.

Helman, R. G. and W. C. Edwards. Clinical features of blister beetle poisoning in equids. Journal of American Veterinary Medical Association. 211: 1018-21, 1997.

Metcalf, C. L. and W. P. Flint. Destructive and Useful Insects. New York: McGraw-Hill Book Company, 1962.

Minks, A. K. and P. Harrewijn. Aphids: Their Biology, Natural Enemies and Control. New York: Elsevier Science Publishing Company Inc., 1988.

Ray, A. C., A. L. Kyle and M. J. Murphy. Etiologic agents, incidence and improved diagnostics. American Journal of Veterinary Resources. 50: 187-91, 1989.

Ray, A. C., L. O. Post and J. C. Reagor. GC/MS confirmation of cantharidin toxicosis due to ingestion of blister beetles. Vet Hum Toxicol. 22: 398-9, 1980.

 

(http://www.ent.iastate.edu/imagegal/coleoptera/blister/0982.11blackblistb.html)

 

 

Blister Beetles

Common name: blister beetles
Scientific name: (Insecta: Coleoptera: Meloidae)

Introduction

The family Meloidae, blister beetles, contains about 2500 species, divided among 80 genera and three subfamilies. Florida has 26 species, only a small fraction of the total number in the U.S., but nearly three times that in the West Indies (Selander and Bouseman 1960). Adult beetles are phytophagous, feeding especially on plants in the families Amaranthaceae, Compositae, Leguminosae, and Solanaceae. Most adults eat only floral parts, but some, particularly those of Epicauta spp., eat leaves as well. A few adults are nocturnal; most are diurnal or show no distinct diel cycle. Since adults are gregarious and often highly colored, they tend to be conspicuous. However, except for first instar larvae (triungulins) frequenting flowers or clinging to adult bees, larval blister beetles are seldom seen. So far as known, all larvae are specialized predators. Larvae of most genera enter the nests of wild bees, where they consume both immature bees and the provisions of one or more cells. Those of some Meloinae, including most Epicauta spp., prey on the eggs of acridid grasshoppers. A few larvae evidently prey on the eggs of blister beetles (Selander 1981). Of the Florida species, Nemognatha punctulata LeConte (misidentified as Zonitis vittigera (LeConte)) has been found in a nest of a Megachile sp. in Cuba (Scaramuzza 1938) and several members of the genus Epicauta have been associated with the eggpods of Melanoplus spp.

Distribution

Fourteen of the Florida species are limited largely or entirely to the Atlantic and/or Gulf coasts of the U.S. Ten species are more or less widely distributed in the central and/or eastern states. Two species occur both in the southeastern U.S. and the West Indies. No species is endemic. Both species ranging into the West Indies belong to South and Central American groups and probably reached the continental U.S. from the islands. A third, weaker faunal link with the West Indies is represented by Pseudozonitis longicornis (Horn), whose group includes one West Indian species and two relictual species in east Texas (Enns 1956, Selander and Bouseman 1960).

Description

Adults are rather soft-bodied, long-legged beetles with the head deflexed, fully exposed, and abruptly constricted behind to form an unusually narrow neck, the pronotum much narrower at the anterior end than the posterior and not carinate (keeled) laterally, the forecoxal cavities open behind, and (in all Florida species) each of the tarsal claws cleft into two blades. Body length generally ranges between 3/4 and 2 cm in the Florida species. Families with which blister beetles are likely to be confused are Oedemeridae (Arnett 1984) and Lagriidae.

Triungulin larvae of Nemognathinae found in flowers or attached to the hairs of bees are sometimes mistaken for those of Rhipiphoridae. In both groups, the body is navicular and heavily sclerotized and there is a definite pattern of setation. Nemognathine larvae are distinctive in having one to two (not four to five) stemmata on each side of the head, an ecdysial line on the thorax, and no pulvilli (bladderlike appendages).

Nemognatha plazata Fabricius, triungulin

Keys to genera for adult beetles and triungulin larvae are given in references (Arnett 1960) and (MacSwain 1956), respectively. Adults of most of the Florida species are described by Enns and Werner (Enns 1956, Werner 1945).

Life Cycle

Eggs are laid in masses in the ground or under stones (Meloinae) or on the food plants of adults (Nemognathinae). Larval development is hypermetamorphic, with four distinct phases.
In the first instar or triungulin (T) phase the larva reaches its feeding site on its own (most Meloinae) or is carried there by an adult bee, to which the larva attaches from a flower (Meloini (not in Florida) and Nemognathinae). After feeding to repletion, the larva, with ecdysis, becomes scarabaeiform and enters a period of rapid growth (first grub phase, FG) that lasts until the end of instar five or six. In some species that prey on bees the FG larva uses only a single cell; in others it digs into nearby cells and devours their contents. In Meloinae the fully fed FG larva generally excavates a chamber apart from the feeding site. In instar six or seven, the larva typically becomes heavily sclerotized and immobile (coarctate phase, C). In this phase the musculature undergoes profound degeneration and respiration is reduced to an extremely low level, permitting survival for more than a year, if necessary. When development resumes the muscles regenerate and, with ecdysis, the larva once again becomes scarabaeiform (second grub phase, SG); at this point it may or may not excavate a pupal chamber. Nemognathinae are unusual in that the SG larva and following pupa and adult are encapsulated by the cast but intact skins of the last instar FG larva and the C larva.

 

Blister Beetle Life Cycle
A = adult, E = egg, T = first instar or triungulin, FG = first grub phase,
C = coarctate phase in instar six or seven, SG = second grub phase, P = pupa

Several alternative developmental pathways have been identified. In response to high temperature, many Epicauta larvae pupate directly from the FG phase or fail to diapause in the C phase; both patterns are conducive to multivoltinism. Rarely, a larva pupates directly from the C phase. Presumably in response to adverse environmental conditions, larvae of several genera of Meloinae can return to the C phase after reaching the SG phase. Most species pass the winter or dry season as coarctate larvae; a few do so as diapausing eggs, triungulin larvae, or adults.

Adults commonly live three months or more. Females typically mate and oviposit periodically throughout their adult lives.

Medical and Veterinary Importance

Blister beetles receive their common name from the ability of their hemolymph to produce blistering on contact with human skin. Hemolymph is often exuded copiously by reflexive bleeding when an adult beetle is pressed or rubbed. Blisters commonly occur on the neck and arms, as the result of exposure to adult beetles attracted to outdoor lights at night. General handling of adults seldom results in blistering unless the hemolymph contacts the relatively thin skin between the fingers. Unless extensive, medical treatment beyond first aid for blistering on humans is probably not necessary. The blistering on the individual shown in the photograph, while uncomfortable, was not painful. The blisters soon diminished on their own.

human blistering

The blistering agent is cantharidin, an odorless terpene (exo-1,2-cis-dimethyl-3,6-ep- oxyhexahydro-phthalic anhydride) occurring elsewhere only in beetles of the family Oedemeridae (Arnett 1984). Cantharidin or cantharides (dried, pulverized bodies of adult beetles) was once employed extensively in human and veterinary medicine, primarily as a vesicant and irritant and is still used in the U.S. as the active ingredient in a proprietary wart remover. Taken internally or absorbed through the skin, cantharidin is highly toxic to mammals. There is an extensive literature dealing with its reputed aphrodisiacal properties and numerous reports of human poisonings, both accidental and deliberate. Cantharides is sometimes specified as the Eurasian Spanishfly, Lytta vesicatoria (Linnaeus); however, other genera, particularly Mylabris and Epicauta, have been more commonly used, especially for extraction of cantharidin. Recorded cantharidin content of adult beetles (by dry weight) ranges from less than 1% to a high of 5.4%. Biological synthesis and function have been largely neglected. It is widely assumed that cantharidin confers chemical protection from predators, but there is little evidence for this. In at least some species, females receive large quantities of cantharidin from males during copulation. In any case, females incorporate the material in a coating applied to the eggs.

Cases of fatal poisonings of valuable horses in Florida, Oklahoma, Tennessee, and Texas by ingestion of blister beetles trapped in baled alfalfa hay (Mackay and Wollenman 1981, Schoeb and Panciera 1979) have revived interest in the pathology of cantharidin toxicosis and led to the development of a highly sensitive technique for detection of the compound (Ray et al. 1979). Poisonings have been traced to adults of Epicauta occidentalis Werner and, possibly, E. temexa Adams & Sel. Neither species occurs in Florida, but a close relative (the striped blister beetle, E. vittata (Fabricius)) and three other species of the genus (the clematis blister beetle, E. fabricii (LeConte); the black blister beetle, E. pennsylvanica (De Geer); and the margined blister beetle, E. pestifera Werner) occur in alfalfa fields here and pose a potential threat if horse owners turn to locally grown alfalfa as a source of hay. Research is available to indicate the amount of cantharidin levels present in common species, as well as the estimated number of beetles necessary to provide a lethal dose to horses (Sansome 2002).

Crop Damage

Several of the Florida blister beetles feed on cultivated plants. Species of Epicauta, particularly the margined blister beetle, E. pestifera, and the striped blister beetle, E. vittata, often damage alfalfa, beet, potato, tomato, and other crops by defoliation. Because of the beetles' gregarious behavior, their attacks can be locally catastrophic. In small gardens, it may be sufficient simply to pick the beetles from the plants.

Insect Management Guide: Vegetables
Insect Management Guide: Field Crops and Pastures

Annotated List of Species

In the following list, geographic distribution outside Florida is not summarized for species that range considerably beyond the Gulf and Atlantic coasts in the U.S. Seasonal distribution is not mentioned for species that are active in the adult stage from spring to late summer or early fall. In general, summaries of food plants do not pertain exclusively to Florida.

Meloinae

Pyrota limbalis LeConte. Washington, D.C., south to Highlands County, Florida. One record at light.

P. lineata (Olivier). Northern Florida, including the panhandle, south to Polk County. August-October. Several Compositae and Gerardia (Scrophulariaceae).

adult P. lineata

P. mutata (Gemm.). Northern Florida, including the panhandle, south to Polk County. Cicuta, Daucus, Eryngium, and several other Umbelliferae.

P. sinuata (Olivier). Coastal Plain from Mississippi to North Carolina; south in Florida to Highlands County. Gerardia (Scrophulariaceae).

Lytta polita Say. Georgia border south to Charlotte and Highlands counties. December-June. Has been taken in large numbers at lights.

Epicauta batesi Horn. Coastal Plain from New Jersey to Alabama; south in Florida to Polk County

E. excavatifrons Maydell. Coastal Mississippi and Alabama and south in Florida to Marion County. September-October. Recorded twice from grass.

E. fabricii (LeConte) - the ashgray blister beetle. Northern Florida, including the panhandle, south to Highlands County. April-May. Commonly on Leguminosae, including alfalfa, Baptisia, bean, pea, and sweetclover; sometimes attacks potato and glandless cotton. Often taken at lights.

adult E. fabricii

E. floridensis Werner. Primarily coastal, from Texas and Oklahoma to New Jersey; probably statewide in Florida. Ipomoea (Convolvulaceae), Schrankia (Leguminosae), and (in captivity) Solanum (Solanaceae).

E. heterodera Horn. Coastal Mississippi to Georgia and south in Florida to Osceola County. September-November. Helenium and other Compositae.

E. pennsylvanica (De Geer) - the black blister beetle. Alachua, Leon, and Marion counties. Wide variety of plants, including many Compositae, Chenopodium (Chenopodiaceae), and such crops as alfalfa, beet, and potato.

adult E. pennsylvanica

E. pestifera Werner - the margined blister beetle. Northern Florida, including the panhandle, south to Indian River County Many Leguminosae and Solanaceae, including alfalfa, beet, egg plant, potato, soybean, and tomato.

E. sanguinicollis Horn. Alachua, Citrus, Sumter, and Brevard counties. Recorded in the literature only from Florida, but I have two specimens labeled "Savannah, Georgia." July and October. Compositae, Schrankia (Leguminosae), and cotton.

E. strigosa (Gyll.). Coastal Plain from Mississippi to New Jersey; probably statewide in Florida. Principally on Compositae, Opuntia (Cactaceae), Ipomoea (Convolvulaceae), and Vigna (Leguminosae). Common.

E. tenuis (LeConte). Described from an unspecified locality in Georgia and subsequently recorded in Florida from Baker and Volusia counties south to Highlands County. May-June.

E. torsa (LeConte). Oklahoma and east Texas, east on the Coastal Plain to Georgia and north to Massachusetts; probably statewide in Florida. April-June. Ilex (Aquifoliaceae), Sapindus (Sapindaceae), and Albizzia, Amorpha, and Robinia (Leguminosae).

E. vittata (Fabricius)- the striped blister beetle. Represented in Florida, where it occurs commonly throughout the state except for the Keys, by the "lemniscate" or southeastern coastal race (Adams and Selander 1979). March-May. Wide variety of plants, including Amaranthus (Amaranthaceae) and such crops as alfalfa, bean, beet, cotton, potato, and tomato. Attracted to lights.

adult E. vittata

Nemognathinae

Tetraonyx quadrimaculata (Fabricius). Trinidad, Lesser Antilles, Puerto Rico, Hispa񯬡, and the U.S. Coastal Plain from northern Florida (Alachua and Putnam counties) to Alabama and North Carolina. Convolvulaceae (Ipomoea) and Leguminosae (Bradburya, Coelosia) in the U.S. and these families and Bignoniaceae, Euphorbiaceae, and Verbenaceae in the West Indies. Reported damaging grapefruit flowers in Puerto Rico.

Nemognatha nemorensis Hentz. North Florida, south to Pinellas and Brevard counties. Several Compositae, including Bidens, Erigeron, Heterotheca, and, particularly, Rudbeckia.

N. piazata Fabricius. Represented in Florida by the nominate race (Mississippi to West Virginia south), which occurs statewide, including the Keys. Cirsium and Tetraognotheca (Compositae).

N. punctulata LeConte. Bahama and Cayman islands, Cuba, Jamaica, and the southeastern U.S. Recorded in Florida only from the Keys and Dade County. Bidens and "thistle" (Compositae). Not common.

Zonitis cribricollis (LeConte). Widely distributed in Florida, south to Dade County Achillea, Coreopsis, Helianthus, and Rudbeckia (Compositae). Rare.

Z. vittigera (LeConte). Represented in Florida, where it occurs south to Highlands County, by the nominate, eastern race. Numerous Compositae and Psoralea (Leguminosae).

Pseudozonitis longicornis (Horn). Kansas and east Texas east along the Coastal Plain to South Carolina; recorded in Florida from Highlands County south to the Keys. March-Jul. At lights. Rare.

P. pallida Dillon. Oklahoma and east Texas east to Florida, where it extends south through Dixie and Alachua counties to Hillsborough County. At lights. Not common.

P. schaefferi (Blatch.). A taxonomically isolated species known only from Florida (Pinellas, St. Johns, and Volusia counties) and Myrtle Beach, South Carolina (Kirk 1969). February-May.

Selected References

• Adams CL, Selander RB. 1979. The biology of blister beetles of the Vittata Group of the genus Epicauta (Coleoptera, Meloidae). Bulletin of the American Musuem of Natural History 162: 139-266.
• Arnett Jr RH. 1960. The Beetles of the United States. Catholic University Press, Washington, D.C., xi + 1112 p.
• Arnett JR RH. (September 2000). False blister beetles, Coleoptera: Oedemeridae. UF/IFAS Featured Creatures. EENY-154. http://creatures.ifas.ufl.edu/urban/medical/false_blister _beetles.htm (19 October 2001).
• Enns WR. 1956. A revision of the genera Nemognatha, Zonitis, and Pseudozonitis (Coleoptera, Meloidae) in America north of Mexico, with a proposed new genus. University of Kansas Scientific Bulletin 37: 685-909.
• Kirk VM. 1969. A list of the beetles of South Carolina. Part I - Northern Coastal Plain. South Carolina Agricultural Experiment Station Technical Bulletin 1033: 1-124.
• MacKay RJ, Wollenman P. 1981. An outbreak of blister beetle poisoning in horses in Florida. Florida Veterinary Journal 10: 11-13.
• MacSwain JW. 1956. A classification of the first instar larvae of the Meloidae (Coleoptera). University of California Publication Entomology 12: i-iv, 1-182.
• Ray AC, Tamulinas SH, Reagor JC. 1979. High pressure liquid chromatographic determination of cantharidin, using a derivatization method in specimens from animals acutely poisoned by ingestion of blister beetles, Epicauta lemniscata. American Journal of Veterinary Research 40: 498-504.
• Sansome D. (29 May 2002). Blister beetles. Insect F@stSheets: Agriculture Series. http://dallas.tamu.edu/insects/old_site/Ent-2006.html (10 August 2003).
• Scaramuzza LC. 1938. Breve nota acerca de dos parásitos de "Megachile sp." (Hymenoptera, Apoidea, Megachilidae). Mem. Soc. Cubana Hist. Nat. 12: 87-88.
• Schoeb TR, Panciera RJ. 1979. Pathology of blister beetle (Epicauta) poisoning in horses. Veterinary Pathology 16: 18-31.
• Selander RB. 1981. Evidence for a third type of larval prey in blister beetles (Coleoptera: Meloidae). Journal of the Kansas Entomological Society 54: 757-783.
• Selander RB, Bouseman JK. 1960. Meloid beetles (Coleoptera) of the West Indies. Proceedings of the U.S. National Musuem 111: 197-226.
• Werner FG. 1945. A revision of the genus Epicauta in America north of Mexico (Coleoptera, Meloidae). Bulletin of the Museum of Comparative Zoology (Harvard University) 95: 421-517.

Author: Richard B. Selander, Department of Genetics and Development, University of Illinois at Urbana-Champaign; and Thomas R. Fasulo, University of Florida
Originally published as DPI Entomology Circular 268. Updated for this publication.
Photographs: Division of Plant Industry; John L. Capinera, University of Florida; and Samuel Grubb
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-166
Publication Date: October 2000. Latest revision: August 2003.
Copyright 2000-2003 University of Florida

Featured Creatures
Department of Entomology and Nematology
Division of Plant Industry
Electronic Data Information Source

 

 

Blister Beetle

Common Name: Blister beetle
Scientific Name: Varies
Order: Coleoptera

Black blister beetle, Epicauta pennsylvanica (DeGeer) (Coleoptera: Meloidae), on goldenrod flowers. Photo by Drees.

Description: Blister beetles vary by species in shape, size (3/8 to 1 inch long) and color (solid gray to black or with paler wing margins, metallic, yellowish striped or spotted). Most are long, cylindrical narrow-bodied beetles that have heads that are wider than the first thoracic segment (pronotum). The wing (elytra) covers are usually soft and pliable. Although over 100 species occur in Texas, common blister beetles include:, the black blister beetle; Epicauta pennsylvanica (De Geer), E. occidentalis (east and central Texas) and E. temexa (south Texas) are mostly orangish-yellow with three black stripes on each of the wing covers (elytra). A west Texas species, Cysteodemus armatus LeConte, has wing covers that are broadly oval and convex, colored black with bluish or purplish highlights.

A striped blister beetle, (Coleoptera: Meloidae). Photo by Drees.

Life Cycle: Complete metamorphosis; hypermetamorphosis. Winter is spent in later larval stages and pupation occurs in the spring. The pupal stage lasts about 2 weeks and adults appear in early summer. Female beetles lay clusters of eggs in the soil. The first stage (instar) larva hatching from the egg (triungulin) is a tiny, active, long-legged larva that seeks the appropriate host. Once there, the larva develops

 

Scientific classification

Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Coleoptera Superfamily: Tenebrionoidea Family: Meloidae Gyllenhal, 1810

 

Blister beetles, Epicauta sp. (Coleoptera: Meloidae), mating on Texas mountain laurel. Photo by Drees.

A Meloid from the Western Ghats

Beetles in the Coleoptera family Meloidae are commonly known as blister beetles. There are approximately 2,500 known species worldwide.

They are known as "blister beetles" because they secrete cantharidin, a poisonous chemical causing blistering of the skin and painful swelling. Cantharidin 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.

Blister beetles are hypermetamorphic, going through several larval stages, the first of which is typically a mobile triungulin. The larvae are insectivorous, mainly attacking

Horia sp. from India

bees, though a few feed on grasshopper eggs; while sometimes considered parasitoids, it appears that in general, the meloid larva consumes the immature host along with its provisions, and can often survive on the provisions alone, thus they do not truly qualify (see Parasitoid for definition). The adults sometimes feed on flowers and leaves of plants, such as in the families Amaranthaceae, Compositae, Leguminosae, and Solanaceae.

 

Classification

 

1.    Subfamily Eleticinae

a.  Tribe Derideini

·       Anthicoxenus

·       Deridea

·       Iselma

·       Iselmeletica

b.  Tribe Eleticini

·       Eletica

c.  Tribe Morphozonitini

·       Ceriselma

·       Morphozonitis

·       Steniselma

d.  Tribe Spasticini

·       Eospasta

·       Protomeloe

·       Spastica

·       Xenospasta

2.    Subfamily Meloinae

Tribe Cerocomini

·       Anisarthrocera

·       Cerocoma

·       Diaphorocera

·       Rhampholyssa

·       Rhampholyssodes

Tribe Epicautini

·       Denierella

·       Epicauta

·       Linsleya

·       Psalydolytta

Tribe Eupomphini

·       Cordylospasta

·       Cysteodemus

·       Eupompha

·       Megetra

·       Phodaga

·       Pleropasta

·       Tegrodera

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

·       Ceroctis

·       Croscherichia

·       Hycleus

·       Lydoceras

·       Mimesthes

·       Mylabris

·       Paractenodia

·       Pseudabris

·       Semenovilia

·       Xanthabris

Tribe Pyrotini

·       Bokermannia

·       Brasiliota

·       Denierota

·       Glaphyrolytta

·       Lyttamorpha

·       Picnoseus

·       Pseudopyrota

·       Pyrota

·       Wagneronota

Unclassified group

·       Australytta

·       Calydus

·       Gynapteryx

Unclassified group

·       Oreomeloe

Unclassified group

·       Pseudomeloe

3.  Subfamily Nemognathinae

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

Unclassified group

·       Hornia

·       Tricrania

Unclassified group

·       Onyctenus

·       Sitaromorpha

4.  Subfamily Tetraonycinae

Tribe Tetraonycini

·       Meloetyphlus

·       Opiomeloe

·       Tetraonyx