Blister Beetle

Courtney sent me this photograph of another porch find.  She said "I gave this critter a little push so I could get into better light for pictures and it curled up on its side and secreted some kind of smelly amber liquid from all its leg joints. I included a picture of that too."  She sent it to Inaturalist where she got an ID as a Meloe oil beetle.   This is the American oil beetle, Meloe americanus.

This is a very distinctive beetle.  The abdomen has the appearance of overlapping plates that are somewhat flexible.  It is iridescent and somewhat bumpy.  The elytra (wing covers) are small and there are no wings under them so the beetle is limited to walking around.  It can be found slowly wandering on flowers.

Oil or blister beetle - C. Reese

The name "oil beetle" comes from the amber liquid it secretes from its leg joints when disturbed.  Another name for the Meloidae family is "blister beetles."  This is because the secretions are not only smelly but caustic, capable of causing skin blisters.  The active ingredient is cantharidin, a chemical that has been used medically to burn off warts which then heal without scarring.  It can be fatal when consumed by livestock and has had a lot of other uses in history including one that we won't go into in a family friendly blog.*

This was enough information, but wandering into the Meloe sp. beetles' fascinating life cycle led me down into a "rabbit hole" for several hours.  "Going down a rabbit hole" is a family affliction for us, "Googling" and following hot links to information we didn't know we needed to know.

"Going down a rabbit hole"  -  To enter into a situation or begin a process or journey that is particularly strange, problematic, difficult, complex, or chaotic, especially one that becomes increasingly so as it develops or unfolds. (An allusion to Alice's Adventures in Wonderland by Lewis Carroll.)  Thefreedictionary.com

The female Meloi beetle lays her eggs on the ground under flowers.  The larvae that hatch will go through several generations before adulthood, the first called the triungulin.

"First-instar larvae climb to the top of a plant as a group, clump together in the shape of a female solitary ground bee, exude a scent (pheromone) imitating the female bee pheromone. When a male bee comes and tries to mate with the clump of larvae, some of these clamp onto his hairs and eventually get to female bees when he mates for real. Impregnated female bees fly off and build nests in burrows; triungulins move to the new nests and feed on honey and pollen stocked by the bee for her own young."  Insectidentification.org

Meloe beetle's stages of life -  Wikipedia

 Meloe larvae on a bee -Wikipedia

The act of hitching a ride on another species is called phoresy.  This is commonly seen on beetles which have mites clinging on them.  Generally thiA s causes no harm to the beetle and in some cases is of benefit (mutualism).  Bess beetles routinely carry mites into their rotten log homes.  Carrion beetles frequently have phoretic mites that will eat the eggs and larvae of flies that compete with the beetles young for dead animals.   

OK, that is way TMI.  I am off to find another rabbit hole.

* More on Canthandrin at this site.
More on their family plan at phys.org
A more recent study from 2018 shows that the pheromones are specific for the bees of different regions.