- Author: Kathy Keatley Garvey
Milkweed bugs gained the nickname of "seed eaters" for primarily eating the seeds of milkweed.
Actually, they are opportunistic and generalists, says Hugh Dingle, emeritus professor of entomology at the University of California, Davis.
They will eat monarch eggs and larvae (milkweed is the host plant of monarchs), as well as the oleander aphids that infest the milkweed.
We recently watched a large milkweed bug (Oncopeltus fasciatus) munch oleander aphids on a narrow-leafed milkweed (Asclepias fascicularis) in our pollinator garden in Vacaville, Calif. Between the milkweed bugs and the lady beetles, aka ladybugs), they absolutely cleaned off all the aphids, the first time in years.
Milkweed without aphids? Unbelievable! That's like macaroni without cheese, a pencil without paper, or a hammer without a nail. It's a "given" that if you grow milkweed, you'll get aphids. Some monarch butterfly enthusiasts kill the aphids with a soapy water mixture (which we've done in the past), but this year, we let biocontrol reign.
It worked wonderfully!
"Milkweed bugs will get protein from wherever they can find it," says Dingle, an insect migration biologist and author of the textbook, Animal Migration: the Biology of Life on the Move. They've been known to feed on insects trapped in the sticky pollen of the showy milkweed (Asclepias speciosa). And on nectar.
Dingle served as a professor at UC Davis Department of Entomology from 1982 to 2002, achieving emeritus status in 2003. National Geographic featured him in its cover story on “Great Migrations” in November 2010. LiveScience interviewed him for its November 2010 piece on“Why Do Animals Migrate?”
A fellow of the American Association for the Advancement of Science and the Animal Behavior Society, Dingle has done research throughout the world, including the UK, Kenya, Thailand, Panama, Germany and Australia.
Dingle is a former secretary of the International Society for Behavioral Ecology and past president of the Animal Behavior Society. He received the Edward A. Dickson Professional Award in 2014 to do research on "Monarchs in the Pacific: Is Contemporary Evolution Occurring on Island Islands? (See news story on Department of Entomology and Nematology website.)
- Author: Kathy Keatley Garvey
If you've been finding more milkweed bugs than monarchs on your milkweed, join the crowd.
Monarchs are scarce--at least around Solano and Yolo counties--but milkweed bugs are quite plentiful. Sometimes you see them massing on milkweed pods as if they're having a family reunion and trying to figure out who's who during an all-you-can eat buffet. They're blood red, in sharp contrast to the green plants.
Have you seen the large milkweed bugs, Oncopeltus fasciatus, and the small milkweed bugs Lygaeus kalmii? Both belong to the seed bug family, Lygaedidae. We recently spotted small milkweed bugs on a patch of showy milkweed (species Asclepias speciosa) in Sonoma.
Milkweed bugs are primarily seed eaters, but they're opportunistic and generalists, says Hugh Dingle, emeritus professor of the UC Davis Department of Entomology and Nematology, an insect migration biologist who also researches migratory monarchs.
"They'll get protein from wherever they can find it," said Dingle, author of the popular textbook, Animal Migration: the Biology of Life on the Move. They eat not only eat seeds, but also monarch eggs and larvae and the immature stages of other butterflies, Dingle told us back in 2016. They eat other small bugs and feed on nectar as well. Some scientists have seen them feeding on insects trapped in the sticky pollen of the showy milkweed. (Read about the opportunist Small Milkweed Bug in the Journal of the New York Entomological Society.)
The bugs feed on the toxic milkweed, rendering them distasteful to predators. Their warning colors (red and black) also tell prospective predators "Leave me alone; I don't taste good. If you eat me, you'll be sorry." They sequester and store cardenolides (cardiac glycosides) from the milkweed.
In the fall, as the seed pods burst open, monarch enthusiasts scramble to collect the seeds for next year, but they usually have to compete with the red invaders.
If they're still around...