distributed within six families and at least nine genera (1:22). It is estimated that worldwide there are over 2,000 different species of cantharidin containing beetles. Over 200 of these species exist in within the United States.
Two species, Epicauta vittata and E. pennsylvanica, are found in the south and southwestern parts of the country (1:22). A serious farm pest, E. vittata is particularly abundant in the summer months. They often infest tomato plants.
In the eastern U.S., three striped species of blister beetle include E. temexa and E. occidentalis (formerly classified together as E. lemniscata). These insects can be found from Florida to New Jersey and may range as far as the midwestern and southwestern states to Colorado, and even northeastern Mexico (9:189).
North American blister beetles can grow to one inch in size. Their coloration is variable (1:22). Typically, the insects are found in fodder and other animal food. They primarily subsist on alfalfa hay. Hay other than alfalfa, however, may also become infested when it contains weeds which the beetles can use for food (e.g., silverleaf nightshade).
Cantharidin toxicosis may be an especially serious problem for livestock (9:190). Peak incidences of cantharidin poisoning in animals are usually observed in late summer and early fall. Typically, a 400 kilogram horse need only eat about 100 three striped beetles to ingest a lethal dose. In addition, considerably smaller numbers of beetles can still cause severe problems.
The highest concentrations of the toxin is found in the beetles' ovaries, soft tissues, and blood (7:592). Pawlowsky and Stein quoted several values for cantharidin content for different species of blister beetle. They observed an average concentration of between 2.6 and 4.3 parts per thousand (11:444). Moreover, research by Bodenstein found concentrations as high as 11 parts per thousand in the South African b...