If you have a large patch of milkweed (right), searching each plant for monarch caterpillars can take forever! When we do extensive searches, we make sure to look over each leaf, both the topside and underside.
However, we can use some telltale signs to make searching faster and take a broader approach to a milkweed patch, especially if you’re just searching for fun. My tip is to focus on the tops of plants for caterpillar activity. First, you’ll want to search for small holes towards the center of leaves (left). These holes are evidence caterpillars have been eating milkweed.
When you see the holes, take a closer look at these plants. The next thing you might notice are small black dots (right). The black dots are caterpillar frass, or poop, another sign of caterpillars eating milkweed and growing after emerging from eggs. After I saw the small holes in the milkweed leaves and frass, I knew I was getting close to finding a caterpillar. I slowly pulled back some leaves, and there it was just underneath the flower (below)! Searching for eggs and larvae can be a great way to explore your garden and natural areas. If you spot a monarch in any life stage (egg, caterpillar, or adult), join other community scientists and report your sightings to Journey North.
If you are searching in your own yard, you can register your monarch habitat with the Iowa Monarch Conservation Consortium’s HabiTally app and note if any monarchs are present. Any reporting helps us track conservation actions and determine how to best conserve monarchs in the future.
Katherine Kral-O’Brien