Chestnut Herbal School

Large Milkweed Seed Bugs

Written and Photographed by Juliet Blankespoor

Large milkweed seed bug (Oncopeltus fasciatus)

I recently photographed some colorful milkweed bugs in my garden and decided to repost a small piece I had previously posted about these gorgeous gregarious insects with the new photos, figuring most of you didn’t read the original essay, and would absolutely love to learn more about these charismatic insects. The large milkweed bug, Oncopeltus fasciatus, is a common inhabitant of the milkweed patch. These insects concentrate cardiac glycosides in their tissues, similar to monarch caterpillars and butterflies, and advertise their toxicity with bright red and black coloration. The large milkweed bug feeds collectively on the immature milkweed seeds while they are still in the pods. With their sucking mouthparts, they inject enzymes into the developing seeds, which liquefies and predigests the contents until it is ready to slurp up.

Oncopeltus fasciatus late instar cluster (immature milkweed seed bugs)

Interestingly, this species is so easy to rear in the lab, that it is the insect equivalent to the lab rat, with countless experiments being performed throughout the land. I even found a scholarly article on milkweed bug husbandry!

Butterflyweed (Asclepias tuberosa) seeds, note the wee milkweed seed bugs hiding in the pod

Butterflyweed flower (Asclepias tuberosa)

Large milweed bug with an immature instar on butterfly weed

Large milkweed bugs in love, wearing pollinia

Notice the yellow do-dads hanging off the feet of these lovebird milkweed bugs. These are masses of pollen, called pollinia. Pollinia are produced in lieu of loose pollen in certain plant families, such as the Orchid (Orchidaceae) and Apocynaceae (Dogbane and Milkweed family). These plants put all their eggs in one basket, by massing copious amounts of pollen in one masse, the pollinium.

Common milkweed (Asclepias syriaca)

Honk if you love large milkweed seed bugs!


Meet The Green Mastermind Behind Blog Castanea:

Juliet Blankespoor

JULIET BLANKESPOOR is the founder, primary instructor, and Creative Director of the Chestnut School of Herbal Medicine, an online school serving thousands of students from around the globe. She's a professional plant-human matchmaker and bonafide plant geek, with a degree in botany and over 30 years of experience teaching and writing about herbalism, medicine making, and organic herb cultivation. Juliet’s lifelong captivation with medicinal weeds and herb gardening has birthed many botanical enterprises over the decades, including an herbal nursery and a farm-to-apothecary herbal products business. 

These days, she channels her botanical obsession through her writing and photography in her online programs, on her personal blog Castanea, and in her new book, The Healing Garden: Cultivating and Handcrafting Herbal Remedies. Juliet and her family reside in a home overrun with houseplants and books in Asheville, North Carolina.

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One thought on “Large Milkweed Seed Bugs

  1. Beautiful glitterati of the bug world! And those babies are as cute as bedbugs! They remind me of my little guy when he was a wee wiggly worm, dressed in his halloween onesy. A little racy though showing bug coitus with those pollinia still on their feet – OOOH LA LA!!!!

    Thanks, Juliet for teaching me what these ubiquitous buggers are – now I can sound like i know what I’m talkin about in the garden!

    And those other photos were fantabulous!


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