Wednesday, September 22, 2010

Large Milkweed Bug

On last Wednesday's Carleton College Arboretum stroll, Erika and I came upon a Common Milkweed that was crawling with orange and black bugs.  Definitely a photographic and blogging opportunity!  The bugs were the wrong pattern for the somewhat similar Elm Bug, and, besides, they infested milkweed.  Googling the words "milkweed bug" took me right to the Large Milkweed Bug, Oncopeltus fasciatus.
As this bug's name implies, all stages of this bug mainly feed on milkweed. In May or June, adults that survive the winter begin to mate. Males and females can be connected for up to ten hours. Females lay about 30 eggs a day during the summer. Nymphs molt up to five times before becoming adults. Because they fed on milkweed sap and seeds, these bugs accumulate glycosides. You may recall Monarch Butterflies do the same thing. Both insects sport bright orange colors, serving as a warning to potential predators that they are distasteful, if not downright poisonous. Animals with such warning colors are often seen in nature, and the acquisition of such patterns is called aposematic evolution.
Most of the information for this blog was gleaned from Wikipedia.


  1. A very striking bug, and certainly new to me.

  2. Wow! I have never seen such a thing. Even though I don't have a good relationship with bugs, these are beautiful!