May 21, 2009
Species of the Week - Large Milkweed Bug
By Rachel Shaw | Posted on May 21, 2009
Brightly colored large milkweed bugs should not be eaten, due to the toxins they acquire from milkweed seeds.
Large milkweed bugs feeding on milkweed - note the different developmental stages present. Source
Large milkweed bugs are easily found on milkweed and dogbane in meadows and fields in the East and Southeast. They feed on milkweed seeds preferentially - though adults can eat other plant foods, such as nectar and juices - and become toxic to predators as a result. This makes them one of the few insects that are able to tolerate milkweed toxins; another is the caterpillar of the monarch butterfly. Both animals signal their poisonous nature with their bright black-and-orange markings.
Fully mature adult. Source
Adults mate soon after they emerge, within the first week or so, and produce eggs in about the same amount of time after that. Female milkweed bugs lay up to 2,000 eggs during the summer, at a rate of about 30 a day, depending on the availability of food. Male milkweed bugs live slightly longer than female ones, but only by about a week. Neither lives more than about a month as an adult.
Nymphs go through five stages of development, moving from pale yellow to orange, developing the black markings and growing wingpads as they age. Eggs also begin as yellow, maturing to orange then bright red. Temperature determines how quickly the eggs and young bugs pass through each stage.
Milkweed pod, showing seeds. Source
Raising large milkweed bugs is relatively easy, as their only requirements are seeds and a regular supply of water. They can feed on seeds other than milkweed; one scientific team used watermelon seeds with the hulls cracked (but not crushed - apparently the insects cannot eat ground food), while another recommends sunflower seeds (again, cracked so the bugs can access the meat). The University of Illinois reminds those who wish to try this that the bugs are toxic and advises, “don’t eat your bugs or allow your pets to consume them.”
Sources:
Bug Guide - General information about these insects; the site is a great finding aid.
Macro images of large milkweed bugs at all stages at cirrusimage.com.
The University of Illinois provides rearing instructions.
“Life History and Respiration of the Milkweed Bug Oncopeltus Fasciatus (Dallas),” by R. Emerson Niswander.
PDF (Don’t choose this one unless you want to download a copy.)
HTML
Video of a large milkweed bug moving about on a climbing milkweed plant.
Comments
oops, sorry—I see you already mentioned that in your first photo caption. I missed the teeny type.
Hey, I don’t mind you calling more attention to it - I think the multi-stage herd (flock? swarm?) thing is pretty cool too.
It took me a long time to figure out what these bugs were, which is slightly surprising, given how distinctive they are. (I guess they were just one more confusing Midwestern creature that I’d never seen before, when I first encountered them.)
These are really cool-looking insects.
OMG! And, like, OMG! I love these insects. You’ve really hit a soft spot for me. Thank you for covering a species most ignore or revile.
I find them pretty cool too - and am surprised to hear that some people don’t like them!
I’m not hugely surprised, given that they are bugs, but still - they don’t bite or sting or eat human food plants, and they are attractively colored. On the other hand, that also describes ladybugs, and an awful lot of people get worked up about those, probably because of the winter swarming phenomenon. (None of my sources mentioned large milkweed bugs as doing that, but since some of them do overwinter, perhaps they do?)
Hard to keep up with my online reading when I only get a brief internet connection every few days, but I’m glad I caught this post. These bugs are very cool. I don’t know if we have them in the Pacific NW. I’ll have to look them up.
I didn’t know black and orange markings signified poison. What kind of animals eat these bugs? Are insectivores known to avoid insects with bright black and orange markings?
Arvind - it’s mostly birds that make the attempt - and after a bird has gotten a mouthful of milkweed bug or monarch butterfly, it avoids all similarly bright insects in the future. The viceroy butterfly, which is not toxic, takes advantage of this by mimicking the coloration of monarch butterflies. Insects like bees and wasps do a similar thing with their yellow and black warning markings, so the “bright colors = painful or untasty” is pretty well established when it comes to things like insects (and poisonous frogs).
Elizabeth - like a number of interesting insects (such as fireflies/lightning bugs), these guys are an east-of-the-Rockies species. If there are any in the PNW, they would have had to have been introduced.
One of the cool things about milkweed bugs is that they hang out in multi-age “herds” (I’m sure there’s a technical term for that?) so it’s possible to see them in all stages of development at the same time, as in this photo.
By Dave Bonta on 2009 05 21