Q: What are these bugs on this milkweed?
A:Β The red and black ones are milkweed bugs. That might seem like a snarky answer but itβs the official common name for these insects otherwise known as Oncopeltus fasciatus. They can also be found on oleander plants, which might explain why the yellow insects are called oleander aphids (Aphis nerii).
Both species are commonly found on milkweed and oleander plants. Insects tend to favor specific plants or plant families when they feed. Milkweed and oleander are relatives from the same plant family and known for their sap that contains cardiac glycosides, which are poisonous. The insects that ingest it as a food source are able to sequester it and become protected to some extent.
If you watch other animals preying on these insects, you may notice they spit them back out. The red and yellow coloration is natureβs way of warning predators to leave them alone but not everyone understands the warning signs without a taste test.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
