All about the larvae

It’s all about the larvae in this Journey North monarch update.

Last week, I wrote that we were still waiting on larva reports from many states where we’d had adults for a while, and that news update proved to be timely, because this past weekend saw several developments. 

In the Midwest, we got our first monarch larva reports from Minnesota and Iowa last week, while Wisconsin doubled its total number of reports.

Minnesota’s first report comes to us from Macey in Kasota on June 1. In Cottage Grove, Minnesota, just outside the Twin Cities, Wojciech reported 14 larvae on June 3.

In Eastern Iowa, Janann reported our first larvae from the Hawkeye State on May 27.

A quartet of sightings also came in from Illinois over the weekend, including one from Brian in Addison, Illinois on June 1.

“I have observed new eggs on two different occasions. The first being on May 15. The second eggs appeared May 24. I didn't see any larvae from the first,” Brian wrote. “I saw see four larvae now on three different plants, common milkweed and swamp milkweed. This is all from milkweed grown in my garden at my residence.”

Out east, we received two caterpillar reports from Connecticut. 

“My first two of the season,” wrote Patty in Derby on May 29. “Earlier than last year.”

In Groton, Fatima reported two the next day, writing, “It has been cool and rainy, but today is a bit warmer (66F) and I am very happy to see that 2 out of the 3 eggs on A. incarnata finally hatched.”

Some science

Monarch caterpillars are quite a marvel of the natural world. In two or three weeks, they go from just millimeters in size to between 2.5 and 4.5 centimeters, growing in mass by as much as 2,000 times!  

After hatching, a monarch caterpillar starts by eating its eggshell (chorion), then eating the fine hairs on the bottom of milkweed leaves before moving on to the leaf itself.  

Between this time and pupating, caterpillars go through five periods between molts, or shedding of the skin, called instars. It's a fascinating process of metamorphosis. Take a look at the photo of the two larvae to the right. One is a first instar, while the other is a fifth. 

To read more about the life cycle, including distinguishing characteristics of the five instars, head on over to Monarch Joint Venture's website.