Wednesday, September 18, 2013

Milkweed Beetles

Almost everyone knows these facts about the relationship between Monarch Butterflies (Danaus plexippus) and plants in the Milkweed (Asclepias) family:

  • Monarch Butterfly caterpillars only eat Milkweeds.  
  • Milkweed plants produce toxic chemicals and that the Monarch caterpillars can ingest those chemical without harm.  
  • The caterpillar stores those chemicals in its body, becoming toxic (and bad tasting).
  • These chemicals stay in the Monarch throughout its life cycle.
  • The orange and black coloring of the adult Monarch is a warning to predators that the Monarch is toxic and tastes bad.  This use of warning colors is known as aposematic coloration.
The Monarch is not the only insect that eats Milkweed plants.  In Mid-Michigan there are two species of beetles that also have Milkweeds as their host plants. (There are also two species of Milkweed Bugs.) The Red Milkweed Beetle (Tetraopes tetrophthalmus), also known as the Milkweed Borer, and the Milkweed Leaf Beetle (Labidomera clivicollis) are both found on milkweeds throughout Mid-Michigan. 

Like the the Monarch Butterfly they can consume Milkweeds without suffering any ill effects and store those chemicals in their bodies - using them as a chemical defense against predators.  Also like the Monarch Butterfly both beetle species display aposematic coloration to advertise their chemical defenses. Both species are orange(or red) and black. 

Red Milkweed Beetle (Tetraopes tetrophthalmus) on Common Milkweed

Milkweed Leaf Beetle (Labidomera clivicollis) on Common Milkweed


  1. The milkweed leaf beetle looks a little like a ladybug.

    1. It does look like a version of a ladybug or more properly a lady beetle, but it is significantly larger. I can speak from experience that the aposematic coloring of lady beetles also advertises chemical defenses that make them taste (and smell) very unappetizing.