Large milkweed bug (Oncopeltus fasciatus)


    The large milkweed bug feeds on the seeds of milkweed plants. In the process, this bug sequesters toxic cardiac glycosides from its hostplant. The bright reddish-orange and black color patterns of the nymphs and adults are aposematic colors advertising toxicity.  The milkweed bug is a member of the order Hemiptera (true bugs), family Lygaeidae (seed bugs).  The development of the milkweed bug from egg to adult is an example of Hemimetabolous development (incomplete metamorphosis).  The young nympths closely resemble the adults, but do not have wings or reproductive organs.
    In the field the female milkweed bug lays her eggs in crevices between milkweed pods.  A female lays about 30 eggs a day and 2000 during her lifetime.  Egg-laying begins 1 to 15 days after mating and peaks at about 20 days.
    At  84 degrees F the egg stage lasts four days.  The color of the egg gradually changes from yellow to deep orange as it nears hatching.  The newly emerged nymph is about the size of a pinhead and is bright orange.  The nymph grows by a series of molts.  The stages between molts are called instars.  There are five nymphal instars, each lasting about six days at 84 degrees F.  The adult lives for about one month.
    As is typical of insects which undergo incomplete metamorphosis, the wing pads begin to appear in the early instar, gradually increase in size at each molt, and become quite obvious in the last instar.  The cast skins of the various nymphal instars are easily seen in the culture vessel.  In the fifth instar, the sexes can be easily distinguised by examining the posterior abdominal segments.  The female has median black spots on the ventral side of the two posterior segments; the male has only one black spot on the last segment.
    The adult bugs are also easily sexed.  The ventral side of the fourth abdominal segment (counting from the thorax) bears a black band in the male and two prominent black spots in the female.  Mating takes place 5 to 12 days after the last molt for females and two to three days for males.  Actual copulation may last for up to 10 hours.

Availability: Milkweed bugs are available now. After you have a cage and supplies ready, contact Liz (eegraham@life.uiuc.edu) to schedule a pickup time (right after class is convenient). We will send you a few milkweed bugs (hopefully at different life stages) in a plastic container, and a few seeds to get you started. You need to find a seed source BEFORE you bring your bug home.

Housing: Large glass jars with cloth tops (secured with a rubber band) make good cages. Make sure the jar is completely clean before you use it. Crumpled paper or paper towels make a good surface for the bottom of the cage and gives the bugs places to hide. Water can be provided from wet paper towels or cotton wick protruding through a hole in the lid of a smaller jar. Make sure that clean, fresh water is always available.  Milkweed bugs do very well at room temperature.

Food: Milkweed bugs in the wild feed on milkweed plants. In captivity, they can be reared on cracked seeds of sunflower, watermelon, squash, cashew, and almond. (NOTE: The seeds must be RAW and UNSALTED. They also must be CRACKED as the insect cannot open the seeds on its own!) We'll provide you with some milkweed seeds to begin. Sunflower seeds are probably best for our purposes.

Remove seeds that are shrivelled or dirty and replace them with fresh ones. DO NOT FORGET TO SUPPLY WATER as your colony will quickly die without it.

Above all, don't eat your bugs or allow your pets to consume them. The toxic compounds sequestered by these bugs will cause profuse vomiting (at the very least) and could possibly kill if enough were consumed.