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
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 (firstname.lastname@example.org)
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
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
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.