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Care Guide: Milkweed Bugs

Living Care Information

Oncopeltus fasciatus

commonly known as
Milkweed Bug

Quick Start Information

  • As soon as your order arrives, open the shipping container and inspect your milkweed bugs.

  • Our milkweed bug colony is active and breeding year round.

  • We provide extra organisms in each package. You will receive at least the number of specimens stated on the container.

  • Eggs are provided attached to a piece of cotton inside a plastic vial. It is imperative that milkweed bug eggs are cared for immediately upon receipt. This ensures a maximum hatch rate.

About the Organism

  • Over the course of their life, these bugs accumulate toxins from feeding on milkweed. This toxin can potentially sicken any predators that ignore their warning coloration.
  • Milkweed bugs undergo incomplete metamorphosis. Except for the color pattern of its body, an immature nymph closely resembles an adult.
  • At night, milkweed bugs tend to form groups with other members of their species.
  • Nymphs undergo 5 developmental stages called instars.
  • Milkweed bugs are found in the wild throughout North America, Canada, the Caribbean, Mexico and Central America.
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Hemiptera
  • Family: Lygaeidae
  • Genus: Oncopeltus
  • Species: fasciatus


Prepare your milkweed bug habitat before your organisms arrive. At 29 °C (84 °F), the egg stage lasts 4 days, so hatching should begin soon after you receive eggs. 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. It takes about a month for the nymph to become an adult. Adult milkweed bugs live for approximately 1 month.


Gallon jars or small terrariums make suitable culture vessels. Place crumpled paper in the bottom of the container to provide a surface for the bugs to crawl on.

Nymph hatchlings are very small and will be able to escape through tiny cracks or holes in the covering. Place a piece of cloth or paper towel between the enclosure and the lid to prevent escapees while still allowing for airflow.


Prepare a small, lidded jar of water with a paper towel or cotton wick protruding through a hole in the lid. Set the jar in the habitat. Do not let paper towel or cotton wick dry out. Feed cracked, raw, unsalted sunflower kernels to both adults and nymphs. Place the seeds in a shallow dish inside the enclosure.

Change the water and seeds approximately every 2 weeks or when they become visibly dirty or moldy. Milkweed bugs will not completely consume the seeds.

Maintaining and culturing

A cotton ball or cheesecloth stuffed in a small jar or cup will provide a substrate for females to lay eggs. Tease the cotton or cheesecloth fibers apart to allow females easier access.

Milkweed bug eggs are oblong. They are initially yellow in color, changing to orange and then bright red immediately before hatching. Milkweed bugs may eat their own eggs, so collect eggs daily and place them in a new culture vessel.

Nymphs are wingless and similar in color to the adults. They appear pale yellow immediately after molting and change to orange as they age.

Cultures should be kept at room temperature. Cages with any signs of mold should be washed with a mild soap or a mild bleach solution.


We strongly recommend giving any unwanted organisms to another individual if you do not wish to keep them. Do not release laboratory-reared insects into the wild. As a last resort, place unwanted organisms in a sealed container in a freezer for 72 hours. Dispose of the organisms as your state or district directs.

If desired, organisms can be preserved in 70% ethanol and stored at room temperature for future examination.


Wash your hands with soap and water before and after working with any living organism.



How often should I change the sunflower seeds?

The nymphs and adults do not completely eat the seeds. Replace the seeds when they become shrunken or dirty. Immediately remove any material that shows signs of mold.

How can I tell male from female milkweed bugs?

In adult bugs, the ventral side of the 4th abdominal segment (counting from the thorax) bears a black band in the male and 2 prominent black spots in the female.

How can I tell nymphs from adults?

The young nymphs do not have wings. As is typical of insects that undergo incomplete metamorphosis, the wing pads begin to appear in the early stages, gradually increase in size at each molt, and become prominent in the last nymph stage.

When will the bugs produce eggs?

Mating takes place 5 to 12 days after the last molt for females and 2 to 3 days for males. Egg laying begins 1 to 15 days after mating and peaks at about 20 days.

Will my milkweed bugs eat anything other than sunflower seeds?

In nature, as their name implies, they eat milkweed seeds. In culture, they will eat cracked seeds of watermelons, squash, cashews, and almonds. Once they have adapted to eating one food, it may take several generations for them to adapt to another.

Need help?

We want you to have a good experience. Orders and replacements: 800.334.5551, then select Customer Service. Technical support and questions: caresheets@carolina.com