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.)
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.
Chemical ecologist Yuko Ishida of Toyama, Japan, a former UC Davis post-doctoral researcher who shared the same lab--and the same bench--in Briggs Hall that Duffey did, is the lead co-author of a cover story recently published in the Proceedings of the National Academy of Sciences (PNAS) about an invasive species of millipede that secrets hydrogen cyanide as a defensive mechanism. (See research paper)
Ishida and Duffey never met but they shared a love of science and chemical ecology, in addition to the same lab.
At the time of his death, Duffey was a professor and vice chair of the UC Davis Department of Entomology. When chemical ecologist/professor Walter Leal joined the UC Davis Department of Entomology faculty in 2000, he occupied the former labs of professors Duffey and Susumu Maeda (1950-1998) and memoralized their lives and work by naming his lab the “Honorary Maeda-Duffey lab.”
Ishida worked in the Honorary Maeda-Duffey lab from May 2001 to November 2007 at UC Davis.
“Yuko loves to tackle challenging problems and he is well prepared to solve them,” said Leal, former chair of the UC Davis Department of Entomology and now with the UC Davis Department of Molecular and Cellular Biology.
Ishida also photographed the millipede, found in southern Japan, for the PNAS cover.
The four scientists all work at the Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, and are affiliated with the Asano Active Enzyme Molecule Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Toyama.
“To discover more efficient and stable HNLs, we focused on the invasive cyanogenic millipede as a bioresource,” the scientists wrote. “The HNL identified from the millipede showed not only the highest specific activity toward benzaldehyde among known HNLs, including the almond HNL in industrial use, along with wide temperature and pH stabilities, but also high enantioselectivity in the synthesis of various cyanohydrins. These properties make it suitable as an industrial biocatalyst. Arthropods are likely to be valuable sources of potential biocatalysts for the next generation of industrial biotechnology.”
“There followed several papers on the biochemistry of HCN production and the production of other defensive compounds in these interesting animals,” they wrote. “After arriving at UC Davis, Sean began a long series of brilliant studies on the chemical mechanisms used by plants to fend off attack by insects and various pathogens. This work centered on resistance in tomatoes, and over the years he collaborated with numerous students and colleagues. Studies analyzed the role of numerous chemicals produced by plants including tomatine, proteinase inhibitors, and various plant oxidative enzymes. Recent studies had included analyses of induced defenses and the interactions of chemicals with the biological agents such as parasitoids and baculoviruses used in various IPM and biological control programs.”
“A constant theme and frequently emphasized message in Sean's work was the fact that chemical-biological interactions were rarely simple and straightforward,” they wrote. “He stressed that in order to understand plant-insect interactions, for example, it was necessary to understand the interactions among plant chemicals, the overall characteristics of the insect's diet, the physiological state of the insect, and the modifiable characteristics of plant and insect. Chemical and biological context and chemical mixture were seen as critical determinants of biological activity; a simple view that natural products functioned merely as "toxins" or isolated defensive factors was often misleading.”
Carey, Dingle and Ullman praised Duffey's "truly interdisciplinary research that included several joint projects with members of the Entomology Department and also with colleagues in the departments of Nematology Ecology and Plant Pathology. We all experienced Sean insisting over and over that interactions are not simple and that one must understand the chemistry, the physiology, and the ecology to really understand interactions between plants, insects, and their pathogens. Sean's legacy is an outstanding record of how to go about studying plant-insect interactions, not just the gathering of data on interactions that occur.”
The legacy continues...