Monarch Watch

Continuing our Monarch Biology series, here is part two of the larva!

Here, we highlight some different aspects on the monarch caterpillar's anatomy throughout this stage and take a look at their eating habits.

Monarch larvae will eat milkweed differently during different growth stages, or instars. In the 1st to 3rd instar, the larva will exhibit a behavior called "trenching," eating only a few layers of the milkweed plant so as not to consume a large amount of sticky sap that can flow out of the plant.

In its 4th instar, the larva will chew in a circular shape to avoid the flow of too much sap while feeding.

During the 5th instar, the larva will sometimes partially chew through a milkweed stem, causing the leaf to hang down. This reduces the flow of sap to the leaf so that the monarch can feed on it, and this technique is called "flagging." A 5th instar monarch will eat voraciously and can consume entire leaves.

Next time you see a milkweed plant, see if you can spot some of these signs of monarch caterpillars feeding!

Leading Photo Credit: Trish Place