Serendipity and Two Checkerspot Butterflies

Baltimore Checkerspot (Euphydryas phaeton)

Lately, winters at the Peggy Notebaert Nature Museum find lots of caterpillars on the museum roof. Many of the species that we are breeding for conservation purposes overwinter as caterpillars. They need to experience the full effects of winter cold in order to complete their development. Carrying caterpillars over the winter has proved to be the trickiest aspect of our butterfly breeding activities. A couple of years ago, we learned a new technique form the Portland Zoo in Oregon that involves holding the larvae outdoors under inverted terracotta pots.

Terracotta pots for wintering caterpillars of an endangered butterfly
(Taylor's Checkerspot) at the Oregon Zoo

The larvae themselves are in plastic containers. We loosely crumple paper towels, place the towels and larvae in the containers, and snap the lids on. The whole affair goes under the terracotta flower pot.

Yogurt container, crumpled paper towel, and caterpillars

Two butterflies that we are currently working with are related species called the Baltimore Checkerspot and the Gorgone Checkerspot. Lat year, we did a trial run of keeping Gorgone checkerspots on the roof under pots. It worked so well that we decided to scale it up with both of these species this year. Last week, we woke up the caterpillars.

Gorgone Checkerspot (Chlosyne gorgone)
Photo: Tom Poklen

We has spectacular success with the Gorgones. Over 80% of the larvae survived the winter. They're now in the lab, munching away on their host plant, which is showy sunflower.

Gorgone Checkerspot Larvae
Wake up sleepyheads!

Gorgone Checkerspot Larva

The story with the Baltimores was not so good. Pot after pot yielded dead larvae. All looked perfect, except they were mummified and hard as tiny rocks. Same conditions, closely related species, completely different results.

Dead Baltimore Checkerspot Larvae

Here's where the serendipity comes in. We place our flower pots on wooden pallets on the museum roof. At some point last winter, one cup of larvae fell out of the pot. It was later found under the pallet. It got less protection from the elements, and the paper towel in the cup was soaked with water. Nearly half of the Baltimore Checkerspot larvae in that cup survuved- the only ones from over 1,200 that went on the roof to do so. Unlike Gorgone Checkerspots that live in dry sandy or gravelly prairies, Baltimore Checkerspots are wetland butterflies. Conditions that are fine for Gorgones turn out to be too dry for Baltimores. If the cup had not fallen under the pallet, we never would have known how to fix this problem.

Robin and Vincent feeding Gorgone Checkerspot and Regal Fritillary larvae

In June, the Gorgone Checkerpots will be used to start a new population at the Nachusa Grasslands. The handful of Baltimores will be released at the Fermi National Accelerator Lab. They will (we hope) join individuals that were released there as caterpillars last fall.

Regal Fritillary (Speyeria idalia) larva

In related butterfly conservation news, our Regal Fritillary caterpillars continue to grow and thrive. We are on track for releasing large numbers at the Indian Boundary Prairies this coming June.