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Tonight’s subject is a largish beetle known as the Iron Cross Blister Beetle. These inch-long insects are prevalent in our local desert right about now and their appearance is absolutely unmistakable. Nothing else looks like them. One of these beetles is unforgettable with its brilliant red head and thorax, its equally brilliant yellow carapace, and the large black cross on its back. An extremely interesting looking and, I might add, rather pretty insect.
Blister beetles eat plant material, particularly new shoots and leaves. They neither bite nor sting. They are also among the most toxic creatures that one can encounter. Pick one up and it will secrete a yellowish fluid that will burn your skin on contact, causing painful blisters. Hence the name “blister beetle.” Consume one at your peril. This insect manufactures a poison known as cantharidin, a highly potent neurotoxin that can be lethal. By reputation, at least, a horse can consume a lethal dose of this poison from consuming as few as a half dozen of these insects as it grazes.
The insect also has a mythological reputation. Reputedly, ground up bodies of Iron Cross Blister Beetles were used to make an aphrodisiac known as “Spanish Fly,” the original date rape drug. Feed a small quantity of Spanish Fly to a woman, goes the legend, and she becomes helpless to resist your advances. Well, probably, she becomes too sick to resist one’s advances. Not terribly erotic, perhaps, but who knows, maybe effective.
Blister beetles are an example of something known as aposematism. The insect’s brilliant colors and pattern are a theoretical warning to would-be predators not to eat this insect. Aposematism is the opposite of camouflage in that the insect is literally advertising its presence as a warning. I’ve attended lectures in which the lecturer says that animals and insects use these bright colors as a teaching mechanism. I’m dubious. How does a small bird, for example, learn not to eat a blister beetle? Birds and other predators don’t get taught by their parents explicitly not to eat these beetles. And, this insect is so lethal that the “lesson” one learns from eating it is to die. Not a very effective learning technique if you ask me. More likely, many would-be predators have an instinctive aversion to the brilliant colors and patterns of this insect. Aversion, in other words, may be hard-wired and not learned.
Photo taken with a Canon 5Diii, 180 f3.5 L Macro Lens assisted by Canon 600EX-RT Speedlite, ISO 100, M setting, f10 @ 1/160.