Through most of this portion of the Rio Grande, there are sweeping canyon walls on either side of the river
I would not have guessed that I would see this black blister beetle while on a canoe trip on the Rio Grande. We were staying in Big Bend National Park for an extended weekend trip. For the last full day activity, we decided to do a half-day canoe trip. This involved a one-hour drive through the park to the Santa Elena Canyon. From there we paddled with the current to the southeast. Through most of this portion of the Rio Grande, there are sweeping canyon walls on either side of the river. If you want to take a break, you need to find a location that has built up a sediment bank along the base of a canyon wall. It was while stopping on one of these banks that I saw this insect.
Black blister beetles have the scientific name Epicauta pensylvanica. They belong to the Meloidae, or burning blister beetle, family. They are also known as black aster bugs. Black blister beetles are uniformly black across their entire body. They grow to be anywhere from seven millimeters to fifteen millimeters long. These beetles can be found throughout much of the United States of America and Canada to the west of the Rocky Mountains. They do have some known occurrences in Mexico as well.
The diet of black blister beetles includes Asteraceae, which include the common flowers: goldenrod and asters. They have been known to damage some crops: beets, potatoes, and tomatoes. During their several larval stages, these beetles are insectivorous, meaning that they subsist mostly on insects. Blister beetles are known to attack bees and to eat grasshopper eggs at this stage.
The name “blister beetle” comes from the Cantharidin that is produced by the beetles in this family of insects. It is a poisonous chemical that can cause blistering of the skin. Humans use this chemical medicinally to remove warts. Other uses of this chemical by humans include harvesting it to create aphrodisiacs, as well as to develop poisons. Some other Epicauta are known to produce chemicals that are toxic to horses. Since these beetles are known to forage on many crops, including alfalfa which is fed to horses, they can lead to the death of a horse if the horse consumes too many beetles.
Other uses of this chemical by humans include harvesting it to create aphrodisiacs, as well as to develop poisons
Did you know?
- The oldest fossil in the Meloidae family dates to around 99 million years ago!
- There are 2,500 known species of blister beetles.
- Some blister beetles practice aposematism, which announces their toxicity to potential predators.
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