Among the milkweed

We have a horse pasture that’s occupied by a horse, Rose, and donkey, Midnight. They are both pushing 40 and have been together for most of that time. They actually came with the farm; the previous owners could find homes for one or the other, but not both, and they are inseparable. Well they are both pretty fat, and can’t nearly keep the pasture mowed by themselves, so we get a lot of weeds. There’s a milkweed patch at the west end that is doing pretty well; the ponies keep the grass down, but don’t touch the milkweed, since it has a profoundly nasty flavor, and this benefits the milkweed nicely.

We don’t see a lot of Monarch butterflies here, a few a day from late May. I think the main migration route is more to the west. Heres a map of sightings from Journey North, and you can see a gap that runs up through Central Ohio.

Journey North map of 2019 peak Monarch migration.

Anyway, I was hoping to see Monarchs hanging out around the milkweeds, and over about 3 hours, saw one, and then two working the milkweed flowers.

Monarch on milkweed blossom

I had assumed that Monarchs were important pollinators of milkweed, but they are not. Milkweed flowers don’t produce pollen grains like I had expected, but bundle their pollen in a little sack, called pollinia. Their nectar attracts many insects, but only a few have the anatomy to (accidentally) grab the pollinia and move it to another flower on another plant. (It needs to be another plant, because milkweed doesn’t do selfing.)

Honey Bee and Japanese beetles working milkweed blossom.
Honey Bee and Japanese Beetles

I snapped this picture of a honey bee busily pollinating while two Japanese beetles busily destroy blossoms. I didn’t know anything about pollinia until I was reading up on monarchs and milkweeds in a really good book on the subject appropriately entitled “Monarchs and Milkweed” (Anurag Agrawal, Monarchs and Milkweed, 2017, Princeton, NJ, Princeton University Press). Well. The wonderful thing about photography is that you will find things in the image that you never noticed in the object. In the picture above, the honey bee has a little gadget stuck on her back legs, which is, sure enough, a pollinium.

Honey Bee and milkweed pollen sac “pollinium

The honey bee is one of the invasive imported species that we actually welcome, so it clearly didn’t evolve with milkweed. So it would be interesting to identify native pollinators. There’s a really good article on the topic at which suggest that honey bees in fact displaced the native bees that evolved with the milkweed.

I did see a variety of insects working the blossoms.

Great Spangled Fritillary

The wonderfully named Great Spangled Fritillary is very common around here, as is the Common Sooty Wing. I doubt either of these guys have the equipment to pollinate milkweed but they enjoy the nectar.

Common Sooty Wing skipper
Wasp mimic fly, genus Physocephala

I thought this guy was a wasp, as it turns out, it’s a fly that mimics a wasp. Worked for me. I also saw several bumble bees, and a pearl crescent butterfly.

You’ll also see various red insects with black markings, sometimes on the blossoms. This little guy is the Red Milkweed Beetle (Tetraopes tetrophthalmus). Not a pollinator, these beetles eat milkweed for breakfast, lunch and dinner. Like Monarchs, they have evolved to manage the toxic sap of the milkweed, which provides them with a terrible flavor that makes them very unattractive to predators.

The “Tetraopus” refers to their four eyes, arranged above & below the antenna.

Milkweed Bug

The Large Milkweed Bug also evolved as a pest to milkweed, and like the milkweed beetles, has aposematic coloration, a cool word I just learned, which refers to coloration that warns predators that they can eat you, but may not enjoy it.

Milkweed bug nymphs

I believe these are Milkweed bug nymphs, a juvenile stage of the Milkweed bug. There is also a Small Milkweed Bug and a Milkweed Leaf Beetle that I haven’t seen yet, but all have characteristic red and black coloration, and live exclusively on milkweed.

Ant tending aphids
Ant tending aphids

Here’s an ant tending aphids on the bottom side of a milkweed leaf. The aphids suck juices from the plant, and ants drink the sugar-rich excrement of the aphids, “honeydew”. If you look closely, you can see a drop of honeydew emerging from the aphid. It seems to have the attention of the ant.

Aphids, Aphis asclepiadis, on milkweed

These are apparently various life stages of the aphids, Aphis asclepiadis, with nymphs and a winged adult. There are two other species of aphids specializing in milkweed that I will be looking for.

Monarchs begin their lives on milkweed. They lay their eggs on the underside of the leaves, in three or four days, a tiny caterpillar emerges. This guy is about 2″ long, maybe 4th instar?

Over the next 10 to 14 days, the caterpillar eats a lot of milkweed, and grows through 5 instars, or molts, until it is 2 to 3-1/2 inches long. Then it forms the chrysalis, and another 10 to 14 days later, an adult Monarch butterfly emerges. The butterfly can eat wherever nectar is served. I often see them working clover in the hay field, also butterfly bush, cone flowers, and the usual butterfly suspects. The adults will return to milkweed to mate and start the cycle over.