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Insects and other arthropods

Milkweed: host plant to a number of insects

Milkweed tiger moth
Milkweed tiger moth
  • Milkweed tiger moth
  • Milkweed tiger moth, last instar
  • Small milkweed bug
  • Common milkweed beetle
  • Milkweed leaf beetle larva
  • Milkweed leaf beetle larva

Because of its toxicity, milkweed isn’t popular with many insects. But some, like monarchs, have found a way around the plant’s defences. These insects form a very special community, one that is unique and exclusive to milkweed. And they all sport bright colours to show that they’re poisonous and to warn off predators.

Milkweed tussock moth or Milkweed tiger moth (L’arctiide de l’asclépiade)
Euchaetes egle

These moths have grey-brown wings and bright yellow, slightly orange abdomens. They are less showy than monarchs, and advertise their toxicity by producing clicks with their tymbal organs on their thoraxes.

Adults are less commonly seen than caterpillars, which permanently live on milkweed, their host plant. Milkweed tussock moth caterpillars are usually found in groups, in late summer. They are definitely worth looking for! They start out their lives as tiny and grey, but grow to about 3.5 cm, covered in numerous black, white and orange tufts of “hair.”

Small milkweed bug (La punaise de l’asclépiade)
Lygaeus kalmi

These colourful bugs have a red X on the top of their bodies, making it easy to recognize them. Like all true bugs, their mouth is an organ that allows them to pierce plant stems and suck the sap. Later in the season, they can also eat the inner portion of milkweed seeds. Because they rarely congregate in large numbers on a given plant, they do not seriously damage the plants.

Common milkweed beetle (Le longicorne de l’asclépiade)
Tetraopes tetrophtalmus

A common milkweed beetle is about 1.5 cm long, and is almost all red, with a few black spots. Like other related beetles, it has long antennae.

Adult common milkweed beetles feed on leaves, but the larvae bore inside the stem and eat the plant’s tissues.

These harmless insects are easy to catch, if you can get them before they drop to the ground! A common milkweed beetle has one other defence mechanism: it produces a sort of stridulation by rubbing areas on its thorax together.

Milkweed leaf beetle (La chrysomèle de l’asclépiade)
Labidomera clivicollis

As adults, these little round beetles are very attractive, with their shiny blue-black heads and thoraxes and orange-yellow elytra covered in variously shaped black spots. The larvae, on the other hand, are somewhat less elegant.

Despite their name, milkweed leaf beetles eat all parts of these plants.

Goldenrod soldier beetle (La cantharide de Pennsylvanie)
Chauliognathus pennsylvanicus

Although these beetles do not live exclusively on milkweed plants, they can often be observed there. They can be recognized by their rather soft beige or brown bodies, their long segmented antennae and their abdomens extending past their elytra (more or less, depending on whether you are looking at a male or a female).

The adults feed mainly on pollen and nectar, while the larvae eat soft-bodied insects.

Aphis nerii
Myzocallis asclediadis
And other species.

Milkweed plants are often hosts to aphid colonies. Most often you will see milkweed aphids (A. nerri). All aphids are piercing-sucking insects, which means that they pierce plants’ stems in order to suck out the sap. They prefer the young parts of plants, and often feed near the tips of stems.

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