Life Among the Milkweeds

Green Immigrant Leaf Weevil

When most people think of milkweeds and the insects that are associated with them, they think of the iconic Monarch butterfly, which subsists solely on these plants in its larval stage. Others may recall the beautiful Red Milkweed Beetle, the black and orange Small and Large Milkweed Bugs, or the fuzzy Tussock Milkweed Moth caterpillars that sometimes gather together in groups of a dozen or more. However, milkweeds are an abundant source of nectar and pollen for many types of insects, and these in turn attract predators searching for easy prey. If you spend some time examining these plants at the height of their flowering season, an amazing secret world opens up, as all kinds of colourful creatures can be found on their flowers and leaves. Here are a few of the colourful and intriguing creatures I photographed in early to mid-July while looking for the more common butterflies and dragonflies.

On July 3rd I spent some time birding and looking for bugs along the Watt’s Creek Path near Shirley’s Bay. I was really hoping to find an Indigo Bunting to add to my year list, but found myself entranced by the bugs instead, starting with a jewelwing damselfly near the creek that flew off before I could identify it. After the jewelwing left, I found myself searching for Monarch caterpillars in the large groups of Common Milkweed along the path, and found one right away:

Monarch Caterpillar

I only saw the one, which surprised me given how abundant these flowers were. I did come across this interesting fly in my search, however, and later determined it is some sort of Signal Fly, a member of the Genus Rivellia. These flies are often difficult to identify from photographs alone; they are quite small, and identification depends on the presence or absence of tiny hairs called setae on the dorsal thorax, as well as the colour pattern of the wings and legs. They get their name from their patterned wings, which they tend to wave around as if signalling other individuals. I didn’t see this behaviour as this individual rested on an unopened milkweed blossom, so I was immediately taken with the unique pattern of its otherwise clear wings.

Signal Fly (Rivellia sp.)

Where there are small, nectar-loving insects there are small, insect-loving predators, and I wasn’t surprised to see this tiny jumping spider lurking on a milkweed leaf. The red on the abdomen stood out to me, as did its large, flea-like jumps from one part of the plant to another. It never did let me in close enough for a macro photo, so I wasn’t able to capture as much detail as I would have liked.

Jumping Spider

The next day I stopped in at the Hilda Road feeder area to check out the milkweeds there. I was particularly hoping to see some Banded or Coral Hairstreaks, both of which I’d had there in the past, and perhaps some interesting dragonflies as well. Unfortunately I didn’t find any of the butterflies or dragonflies I was searching for, although a beautiful, fresh male Virginia Ctenucha moth caught my interest instead. I love the combination of the yellow head and metallic blue body, although the body is usually hidden by its dull brownish wings.

Virginia Ctenucha moth

You can tell it’s a male by the feathered antennae – female moths lack the feathering.

Virginia Ctenucha moth

The following weekend I was still hoping to see some hairstreaks, and went to the Bruce Pit where I also hoped to see some Gray Tree Frogs. I was shocked to see that the area at the base of the toboggan hill had been almost entirely mowed, with very few flowers or milkweeds present. This was where I had seen a few Acadian Hairstreaks last year, and was unable to find a single one. I continued my walk around the pond, and found a few milkweed plants growing inside the fence on the south side of the trail. There I found a spider – possibly a jumping spider of some sort – feeding on a Rose Chafer Beetle on a milkweed leaf. I hadn’t seen such a thing before, so I stopped for a few pictures.

Spider with Rose Chafer Beetle

From there I drove over to Shirley’s Bay, where I observed this tiny, colourful beetle on the dyke. It has no common name, but is a member of the family Carabidae, or Ground Beetles. Although not visible in this image, this species has large jaws used to eat small insects, including caterpillars.

Calleida punctata

This pretty green weevil was observed on the Swamp Milkweed in my own backyard. I believe it is a Green Immigrant Leaf Weevil (Polydrusus formosus), a non-native species which originates from Europe. It most closely resembles the native Pale Green Weevil (Polydrusus impressifrons), which has a larger gap between the eyes on the dorsal side, and a longer temple (the space between the eye and the place where the head attaches to the thorax). The Pale Green Weevil has a gap which is larger than the diameter of the eye, whereas the the temple is less than the diameter of the eye in the Green Immigrant Leaf Weevil. Of course, the Pale Green Weevil is paler in colour, and appears to have fewer black markings than the Green Immigrant Leaf Weevil.

The Green Immigrant Leaf Weevil is considered invasive in some parts of North American as it displaces native weevil species. Weevils are beetles, and therefore members of the Order Coleoptera. They are further categorized as members of Family Curculionidae, the Snout and Bark Beetles.

Green Immigrant Leaf Weevil

The only butterfly I managed to photograph on milkweed in that time was this pretty little Dun Skipper on some Swamp Milkweed at the Beaver Trail. The brown wings and golden head help to identify this otherwise drab butterfly, but I find them quite pretty, especially those individuals that have just emerged with the sun shining on them on just the right angle!

Dun Skipper

It’s no coincidence that insect diversity is at its peak just as the milkweeds come into bloom; many other insects other than Monarchs depend on their flowers and leaves for sustenance. I was thrilled to find so many interesting and colourful insects among these plants these past few weeks, and will continue watching the milkweeds as long as their flowers continue to bloom.

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