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.)
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...
That's way we were excited to see National Public Radio's Nell Greenfieldboyce generate a recent piece on "Bugs Abound: If You Think the Skies Are Crowded, You Have No Idea."
She touched on a newly published study in the journal Science, which found that more than 3 trillion migrating insects fly over south-central England each year.
More than 3 trillion!
Dingle, author of the popular textbook, Animal Migration: the Biology of Life on the Move (Oxford University Press), is one of the world's experts on animal migration. National Geographic featured Dingle in its cover story on Great Migrations in November 2010. LiveScience interviewed him for its November 2010 piece on Why Do Animals Migrate?
Dingle agrees that many migrating insects receive little attention. "Certain insects like locusts and the monarch butterfly, have gotten a great deal of attention," he told Greenfieldboyce. "But perhaps because of all that attention on these big charismatic insects, the huge migrations that occur in lots and lots of other insects, all the way down to tiny aphids, are certainly not as well known by the public, and may not even be as well known by scientists."
And scores of butterfly enthusiasts flock there, too, to admire, photograph and monitor them. It's good to see the increasing human population banding together to help save the declining monarch population.
As for the NPR piece, Greenfieldboyce gave a little press to one of the least publicized insects, the marmalade hoverfly, which she described as a "a small, insignificant-looking creature."
But don't consider the hoverfly "inconsequential." It's not only a long-range migrant that travels at great speeds and for hundreds of kilometers in a single flight, but it's a beneficial bug: it eats aphids and pollinates crops as well as wildflowers. It winters in the Mediterranean but returns to England in the spring.
Check out the paper in Science, "Mass Seasonal Bioflows of High-Flying Insect Migrants," for more information on migrating insects and you'll see why the NPR headlined its piece "Bugs Abound: If You Think the Skies Are Crowded, You Have No Idea."
The researchers' 10-year project of monitoring the migration of large and small insects over the southern United Kingdom yields incredible information. That's why we now know what they know--that 3 trillion of these migrating insects fly the friendly--and not so friendly skies--every year.
It's getting pretty crowded there.
All summer and into fall, we spotted the familiar reddish, black and white bugs scurrying around on our showy milkweed, Asclepias speciosa, and tropical milkweed, Asclepias curassavica.
Showy bugs on showy milkweed.
The ones we saw: the Small Milkweed Bug, Lygaeus kalmii. Like its name implies, it's small, about half an inch long.
They're primarily seed eaters, but they're opportunistic and generalists, says insect migration biologist Hugh Dingle, emeritus professor of the UC Davis Department of Entomology and Nematology, author of the popular textbook, Animal Migration: the Biology of Life on the Move. "They'll get protein from wherever they can find it," he said. Dingle, whose research includes migratory monarchs, said the milkweed bugs not only eat seeds, but they also eat monarch eggs and larvae and the immature stages of other butterflies. Forever the opportunists, they eat other small bugs as well--if the opportunity arises. And they feed on nectar, too.
Some scientists have seen them feeding on insects trapped in the sticky pollen of the showy milkweed.
The bugs, it seem, have few predators. They feed on the toxic milkweed, which makes them distasteful to predators, prey to avoid. Their warning colors (red and black) strike home that fact.
In the fall, as the seed pods burst open, it's a horticulture/culinary war between the milkweed growers and the milkweed bugs. Both want the seeds: the humans to plant them and the bugs to eat them.
(Note: Research shows that the milkweed bug also feeds on other plants. Read about the opportunist Small Milkweed Bug in the Journal of the New York Entomological Society.)
(Editor's Note: An earlier announcement indicating that this seminar was postponed was an error. It will be held at the same time, date and place.)
Those amazing monarch butterflies!
We're looking forward to a seminar on UC Davis-based research on monarchs in the Pacific Islands.
"The monarch butterfly is an iconic insect in North America largely because of its long-distance migration to precise overwintering sites in Mexico and subsequent return," says Hugh Dingle, emeritus professor, UC Davis Department of Entomology and Nematology.
"Less well known is the fact that it has been introduced to islands across the Pacific and into Australia in the last 200 years or so," he points out. "This presents a great opportunity to study contemporary evolution and adaptation along a migrant/resident axis."
Dingle and graduate student Micah Freedman of the UC Davis Population and Biology Group will present a seminar, sponsored by the UC Davis Department of Entomology and Nematology, on Wednesday, Nov. 9, on "Monarchs in the Pacific: Contemporary Evolution or Local Ecology?" The seminar, open to all interested persons, will take place from 4:10 to 5 p.m. in 122 Briggs Hall, Kleiber Hall Drive. Plans call for video-recording the seminar for later posting on UCTV.
"Here we assess orientation capabilities in island residents vs California migrants and patterns of wing shape presently and over time (from museum collections) for comparison to migrants and residents in North and Central America and the Caribbean," Dingle says in the abstract. "This is a work in progress so queries, suggestions, and critiques will be welcomed."
Dingle, who received his bachelor's degree in zoology from Cornell University and his doctorate in zoology from the University of Michigan, served on the faculty of the UC Davis Department of Entomology (now the UC Davis Department of Entomology and Nematology) from 1982 to 2002, achieving emeritus status in 2003. He is a past president of the Animal Behavior Society and former secretary of the International Society for Behavioral Ecology. Following his retirement, he lived in Brisbane, Australia until 2010, accepting an honorary appointment at the University of Queensland. He returned to Davis in 2010 and shares space in Professor Sharon Lawler's lab.
Dingle published the second edition of Migration: The Biology of Life on the Move (Oxford University Press) in November 2014. It is the sequel to the widely acclaimed first edition, published in 1996. National Geographic featured Dingle in its cover story on Great Migrations in November 2010. LiveScience interviewed him for its November 2010 piece on Why Do Animals Migrate?
Freedman, a graduate student in the UC Davis Center for Population Biology for the last two years, is a graduate of Cornell. He received his bachelor of science degree in entomology and plant sciences.
Dingle speculates that the monarchs arrived in the Pacific Islands with their host plant, milkweed, which was valued at the time for its medicinal properties. Some of the islands are extremely isolated, he said.
An analysis of a monarch population in Hawaii shows that resident monarchs have shorter, broader wings than the long-distance migrants, Dingle says. The Hawaii butterfly wings were shorter than the eastern U.S. long-distance migrants, but “not so short-winged as the residents in the Caribbean or Costa Rica, which have been present in those locations for eons, rather than the 200 years for Hawaii.”
“If there are indeed wing shape changes associated with evolution in isolation, are there other changes that may have occurred under selection and local adaptation for residency?” Dingle wonders. “Are there other changes that may have occurred under selection and local adaptation for residency? Examples of such traits might be changes in flight muscle physiology, changes in photoperiodic diapause response, changes in the characteristics of orientation ability and its relation to antennal circadian rhythms, or changes in the reproductive capacity or tactics (re-colonization of ‘empty' habitats is no longer part of the life cycle).
“Diapause and fat storage, necessary to support migration, are triggered by short photoperiods,” Dingle said, “and the butterflies orient using a sun compass synchronized to a circadian rhythm in the antennae." Overwintering sites in North America include the Transvolcanics Mountains of central Mexico, and the California Coast, particularly Santa Cruz, Pismo Beach, and Pacific Grove.