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Large Milkweed Bug

Common Name: Large Milkweed Bug.

Scientific Name: Oncopeltus Fasciatus.

What to look for?  Think Halloween in July! Distinctive black and reddish-orange. And look for a slender, winged insect. The Large Milkweed Bug has a reddish-orange body. The wings are also reddish-orange and have black tips. There is a black diamond shape on the thorax. The Large Milkweed Bug has a conspicuous broad, black band across their back. And on their face is what has been described as a red “mask”. They have six legs and two antennae.

Where can they be found at Carillon Stonegate Pond? For only a month or so during the summer, the Large Milkweed Bug may be found on some of the milkweed plants that grow around Carillon Stonegate Pond and over at Stonegate Park.

How big are they? The Large Milkweed Bug averages approximately three-fourths of one inch in length.

What are their flight patterns? Large Milkweed Bugs can fly well and may fly long distances in search of suitable plants and, for those in northern areas, during migration.

How else do they behave? Behaviors to deal with predators are somewhat moot. With their reddish-orange and black coloration serving as a warning, Large Milkweed Bugs are poisonous due to the toxic cardiac glycosides in the milkweed that they eat. Predators quickly develop a strong avoidance reaction to Large Milkweed Bugs. Although, when alarmed, Large Milkweed Bugs will drop off the plant into the thicket of grasses at its base, where they will hide until it is safe to return.

What’s for dinner? The Large Milkweed Bug feeds only on milkweed seeds and the nectar. Large Milkweed Bugs insert their long slender beak into the ripening milkweed seeds. After injecting digestive enzymes into the seed, they suck the newly liquefied food through their straw-like beak. Adult Milkweed Bugs do not, otherwise, appear to damage flowers, vegetable gardens, or field crops.

Where do they take up residence? The Large Milkweed Bug lives throughout the U.S., up into southern Canada and down into Mexico. They reside in any habitat that supports milkweed plants.

When and where do they breed and nest? Adults overwinter and wait for spring before emerging. Female milkweed bugs lay as many as 50 eggs per day in small clusters. The eggs are light yellow, then turn reddish before they hatch in about five (5) days. The round nymphs start out a bright red with black antennae.  As the nymphs mature, they begin to gain black spots, develop short black wing coverings, and begin turning orange.  The nymphs develop and grow during five molts. The Large Milkweed Bug emerges from the fifth and final molt as an adult. The slender, mature adult form is black and reddish-orange. Adults can mate a week or so after the last molt, and a week to two weeks later, females start to lay eggs.

Where do they migrate? The northern populations of Large Milkweed Bug are highly migratory.

Do they make any interesting sounds? No.

Interesting Facts About the Large Milkweed Bug:

  • Milkweed bugs are true bugs, whereas, beetles, moths, flies, and butterflies are not. Bugs and insects are similar in several respects: six legs, three body parts (head, thorax, and abdomen), and two antennae. But true bugs (order Hemiptera) do not have mouths for biting and chewing food; instead, they have a tubelike beak for sucking fluid.

  • Milkweed bugs store their tubular beak beneath their body.

  • Milkweed seeds seem to be the only host food of the milkweed bug.

  • According to the “BugLady”, the metamorphosis the the Large Milkweed Bug is termed “simple” or “incomplete” because they hatch looking like mini-adults, growing in size and adding wings as they molt (they molt five times). Rather than having a pupal stage, they simply step out of their final nymphal skin as adults.

For more information on the Large Milkweed Bug and sources of information used in this blog (these are the several of the sources that I am using to learn as I blog), please visit The BugLady at University of Wisconsin Milwaukee Field Station, Missouri Botanical Garden, and Insect Identification for the Casual Observer.

The Carillon at Stonegate community is very fortunate to have a variety of wetland, forest and prairie environments conducive to a variety of birds and other wildlife, insects and plants. Our community and the Kane County Forest Preserve do an exceptional job in maintaining this natural environment – both for the benefit of the birds and wildlife and for our residents to enjoy.


Take a hike and see what you can find – and identify!

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