Anyone lucky enough to find monarch eggs and see them hatch, knows the caterpillars come into the world hungry.

They need the food to fuel their growth. Over a 15-day span, monarch caterpillars increase their body mass by 2,000 percent.

Ten days after hatching, the caterpillars get really hungry.

Keith Anderson has kept track of several generations of monarchs, from egg to butterfly. Collecting monarch eggs, hatching the caterpillars and assisting them through chrysalis is somewhere between a hobby and an obsession for him each spring and summer.

Last week, Anderson had tips on collecting and protecting caterpillar eggs through hatching. After that, it’s time to keep the caterpillars fed.

To make sure caterpillars don’t become food for other caterpillars, Anderson keeps recently hatched caterpillars in compartmentalized containers. Pill boxes, tackle boxes or sewing kits will work. He places segments of milkweed leaves atop moist paper towels. The leaves provide cover and food for the caterpillars.

The compartmentalized containers help him keep track of the tiny hatchlings and keeps them from wandering — much.

As Anderson worked to transfer four- and five-day old caterpillars into a larger habitat, he came up with 24 of 25 he had placed in the container. A few minutes of searching through leaf debris, the missing caterpillar was found hiding on a seam of the container.

“That’s good news,” Anderson said. “I’ll sleep tonight.”

Once the caterpillars are four or five days old, he puts them in mesh containers with whole stalks of milkweed. Mesh laundry hampers serve his caterpillars’ needs. If he moved them into the hampers any sooner, the caterpillars would crawl through the holes in the mesh — they’re that small.

Anderson placed the caterpillars — most of which were still clinging to leaf segments from the tackle box — into the hampers with five 10-inch stalks of milkweed.

“They’ll find their way to new leaves and be quite happy about it,” he said.

That’s where the caterpillars will live until they’re ready to go into chrysalis. At about day 10 after hatching, the caterpillars’ growth and appetite go into high gear.

“When these 25 get to day 10 or 11, those stalks I put in there now wouldn’t last a day,” he said.

For anyone thinking about trying to raise caterpillars themselves, Anderson suggests making sure to find a good source of milkweed. Anderson, who cultivates multiple varieties of milkweed in various rain gardens in his yard, said in the past he has needed to borrow extra milkweed from a neighbor to keep the caterpillars fed.

He advises to cut milkweed stalks just above the lowest pair of leaves on the plant. Two more stalks will sprout from the plant if you leave at least a pair of leaves.

“It’s kind of a renewable resource,” he said.

Anderson cautions to avoid milkweed plants that have treated with insecticide, which would kill the caterpillars. He also avoids mixing caterpillars of different ages. Large caterpillars have been known to find their tiny siblings tasty.

“You want to feed them milkweed, not to each other,” he said.

Expect your caterpillars to go into chrysalis at about day 16. Ten days after that, it’s time to expect butterflies.

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General Assignment Reporter

John joined the Post Bulletin in May 2018. He graduated from the University of Iowa in 2004 with degrees in Journalism and Japanese. Away from the office, John plays banjo, brews beer, bikes and is looking for other hobbies that begin with the letter “b.”