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Many beetle species are known for growing to an alarmingly large size. Some examples of supersized beetle species include the hercules beetle, the large black beetle and the giant stag beetle. Large-bodied insects often put a scare into those who have a fear of creepy-crawlies, but even the largest beetle species are typically perceived as harmless insects. However, it may not be wise to dismiss common backyard beetle species, like ladybugs, as friendly or laid back insects, as multiple beetle species in the US are capable of secreting a corrosive substance that significantly burns human skin. This chemical substance is known as “cantharidin”, and its toxicity is on par with strychnine and cyanide. It may surprise many people living in the northeast to learn that several cantharidin-secreting beetle species are abundant in backyard lawns and gardens in the state. These potentially dangerous beetles are commonly referred to as “blister beetles”.

The particular blister beetle species that most residents of the northeast have likely encountered at least once within their yards are not likely to invade a house, but they are known for swarming in large number along the edges of garden beds and around structural foundations. Blister beetle species in the US generally belong to the Meloidae family, and the most commonly encountered species that have also been documented as causing serious burns, skin conditions and other medical issues in the northeast include the black blister beetle, the striped blister beetle, the margined blister beetle and a few species belonging to the “oil beetle” group of blister beetles.

The amount of cantharidin produced by blister beetles varies from species-to-species, but even the smallest secretions can easily contain at least .5 to 1 milligram of cantharidin, which is enough to kill a large horse. The estimated lethal dose of cantharidin for humans is somewhere in between 60 and 80 milligrams. Most medically significant cases of cantharidin exposure see victims developing varying degrees of dermatitis between 24 to 48 hours after exposure. Most cases of cantharidin exposure occur after residents accidentally make contact with blister beetles in residential lawns and gardens. The burn injuries caused by these beetles can appear as pus-filled abscesses or lesions, and other serious medical conditions or even death can result if cantharidin makes contact with mucous membranes within eye sockets, oral cavities or intestinal lining.

Have you ever heard of blister beetles before? Do you know of any other potentially dangerous beetle species?