Life in the Milkweed Patch

Monarch caterpillars are utterly dependent on milkweed, as everyone knows. No milkweed, no monarchs. However, the milkweed patch is a vibrant community, supporting not only monarchs but a diversity of other creatures.

Like monarch caterpillars, some come to eat milkweed leaves, though only a few insects can stomach a milkweed’s chemical defences. These include two beetles, two varieties of milkweed bugs, milkweed tussock moth caterpillars and orange-coloured aphids.

Some insects, such as honeybees, arrive to feed on milkweed nectar. They are joined in this sugary quest by various flies, wasps, moths and butterflies. Other creatures simply use the milkweed’s broad leaves as convenient platforms to hang out. Katydids and grasshoppers rest on the leaves. Most are camouflaged by their milkweed-leaf colour.

Unsurprisingly, all these milkweed visitors attract predators – an array of hungry animals that include spiders, treefrogs, stinkbugs and praying mantids. Most of the insects that feed upon milkweed advertise their toxicity the same way monarch butterflies do, with brilliant orange bodies set off by black markings. This is called “aposematic” colouration – a universal warning to predators to back off.

The yellow-black patterning of a monarch caterpillar serves the same purpose, but alas, this aposematic colouration seems only to deter vertebrate predators, such as birds.

A rogue’s gallery of invertebrate predators feast on monarch caterpillars, killing the vast majority. Spiders and stink bugs are among those unaffected by the toxins monarch caterpillars harbour.

A milkweed patch thrums with life, full of moths, spiders, butterflies and amphibians. I’ve mentioned only a sample of the creatures that call a milkweed patch home. There are many more.

The interaction between monarchs and milkweed is the best-known one from our perspective, but it is only one of many relationships the milkweed patch nurtures.