BUG OF THE MONTH OCTOBER 2009: Large Milkweed Bugs

Unidentified Milkweed Bug?
September 26, 2009
I came across these bugs while working on one of our nature preserves. I have seen the bug before but not in this context. There were several of these inside of the seed head of a couple milkweed plants. What is this bug and what is its ecological relationship with milkweed?
Derek Rogers
Nissequogue, New York

Large Milkweed Bugs
Large Milkweed Bugs

Hi Derek,
This is a group of Large Milkweed Bugs, Oncopeltus fasciatus.  The winged individuals are the adults and the others are immature nymphs.  The food plants are plants in the Milkweed and Dogbane families.  The insects feed on the juices of the seeds of the plants and will not harm the plants, and adults also take nectar.  According to BugGuide:  “In the course of feeding these bugs accumulate toxins from the milkweed, which can potentially sicken any predators foolish enough to ignore the bright colors which warn of their toxicity.”  We found a nice Milkweed Bug Information page posted by the University of Arizona that has useful information.  This is the third letter with an identification request for the Large Milkweed Bug that we have opened today.  Your photo is quite beautiful and we are selecting your letter and photo as the Bug of the Month for October 2009.  Throughout the month of October, it will remain at the top of our homepage.

Hi Daniel,
I would be honored to have my photo posted for the October bug of the month. Thank you for this information and your quick response. I am very impressed with the web site. I do nature preserve management for The Nature Conservancy and often come across interesting insect specimens. I will surely be in touch.
Derek Rogers

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