Monarchs lay their eggs on the underside of milkweed leaves--generally--but we've seen them on stems and on the leaf edges. They usually deposit a single egg beneath the leaf, but we've spotted as many as four on one leaf. They secrete a glue so the egg will adhere.
Color? They're a creamy yellow with narrow longitudinal ridges from the top to the bottom. Size? About 0.9 to 1.2 mm long, or about the size of a pinhead.
They hatch about 3 to 4 days after they're laid. Then you'll see the black-headed tiny larva or caterpillar eating its shell before it begins devouring the leaf.
Some folks confuse the sap-sucking yellow oleander aphids with the monarch eggs. Or the yellow eggs of the lady beetle, aka ladybug. So we took a few images of them.
In our family pollinator garden in Vacaville, we've collected about 250 monarch eggs or caterpillars this year, and the mamas are still laying eggs! We're not the only ones who like monarchs. We try to collect the eggs before the predators and parasitoids get them. Predators include lady beetles (ladybugs), spiders, milkweed bugs, lacewings, and wasps. Tachinid flies and other parasitoids lay their eggs in or on the immature monarchs or deposit their eggs on a leaf that the caterpillar eats. The fly larvae develop inside the living host, killing it. Note: tachinid flies are considered beneficial insects when they lay their eggs in such pests as cabbageworms.
We grow five species of milkweed:
- Tropical: Asclepias curassavica
- Narrowleaf: Asclepias fascicularis
- Showy: Asclepias speciosa
- Butterfly weed: Asclepias tuberosa
- Swamp milkweed: Asclepias incarnata
But back to the question: how can you tell the difference between an oleander aphid and a monarch egg? They are so tiny and both are yellow! Basically, the aphid has legs and it moves! Some aphids are winged and fly. Another clue: aphids cluster together; you won't find monarch eggs in a cluster.
Note that the lady beetle lays her eggs in clusters, so if you find a cluster of eggs, those aren't monarch eggs.
Lady beetles, aka ladybugs, are not the only insects that feed on aphids.
So do the soldier beetles, family Cantharidae. They are sometimes known as leatherwings.
You may also have a good friend, the soldier beetle.
Wikipedia tells us that their color pattern is reminiscent of the red coats of early British soldiers.
So here are all these milkweed bugs clustered on a showy milkweed leaf, Asclepias speciosa. It's early morning and the red bugs are a real eye opener.
They're seed eaters, but as Hugh Dingle, emeritus professor of entomology, UC Davis Department of Entomology and Nematology says: "They are opportunistic and generalists." They not only eat seeds, but monarch eggs and larvae, as well as the oleander aphids that infest the milkweed.
But wait, one of these is not like the other.
A lady beetle, aka ladybug, photobombs the scene. It sleeps with them and eats (aphids) with them. They are sharing the same food source: oleander aphids.
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.)
Let's hear it for biocontrol.
You've seen lady beetles, aka ladybugs, preying on aphids.
But have you seen an assassin bug attack a spotted cucumber beetle?
How about a crab spider munching on a stink bug?
All biocontrol, part of integrated pest management (IPM).
If you access the University of California Statewide Integrated Pest Management Program (UC IPM) website or more specifically, this page, you'll learn that "Integrated pest management, or IPM, is a process you can use to solve pest problems while minimizing risks to people and the environment. IPM can be used to manage all kinds of pests anywhere–in urban, agricultural, and wildland or natural areas."
Or, UC IPM's more in-depth definition:
"IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and nontarget organisms, and the environment."
Think of biocontrol as beneficial: "Biological control is the beneficial action of predators, parasites, pathogens, and competitors in controlling pests and their damage. Biological control provided by these living organisms (collectively called "natural enemies") is especially important for reducing the numbers of pest insects and mites, but biological control agents can also contribute to the control of weed, pathogen, nematode or vertebrate pests."--UC IPM
Yesterday we witnessed an incredible case of biocontrol in action.
At Bodega Bay's Doran Regional Park, Sonoma County, we spotted a great blue heron stepping stealthily through a thatch of ice plant in the Jetty campground. It was 6:30 in the morning. As campers slept in their recreational vehicles a few feet away, the great blue heron just kept stepping silently through the ice plant. One step. Another step. And another.
And then it happened. Its long sharp beak speared a rodent. Yes, they eat rodents. It crunched the body from head to toe, breaking the bones, and then swallowed it whole.
Not a pretty picture, but a simple case of biocontrol, compliments of a hungry heron.