Warning!  Before you read any further, I should warn you that some of the content of this post is for mature audiences only.

On May 18 I joined a group from the American Entomological Society to do an insect survey at Bowman’s Hill Wildflower Preserve. As we fanned out across the meadow, one of the participants found dozens of caterpillars feeding on plants in the wet part of the meadow.

They turned out to be Baltimore Checkerspot (Euphydryas phaeton) caterpillars eating the leaves of Turtlehead (Chelone glabra).

Baltimore Checkerspots are reported to use a few different species of plants as food for their caterpillars, particularly in their later growth stages.  But their preferred food plant is Turtlehead. This plant contains iridoid glycoside chemicals which enhance the caterpillars’ growth and makes them distasteful to birds. Both the caterpillars and the resulting adult butterflies benefit from this protection, and their bright black, white, and orange coloration act as a warning to advertise their toxicity to potential predators. It helps to fend off attempts to eat them.

Given the early date, the caterpillars were almost certainly individuals that had spent the winter there in the meadow.

On June 16, almost a month after the initial caterpillar sighting, I saw two adult Baltimore Checkerspot butterflies for the first time, not far from where we saw the caterpillars.

A week later, there were at least 10 individuals in the same general vicinity. They spent most of their time perching fairly low to the ground, either basking or advertising for a potential mate. Most flights were short and fairly low.

Occasionally I saw a butterfly drinking nectar from Indian Hemp (Apocynum cannabinum) or White Clover (Trifolium repens).

Ok, this is where things start to get a little racy.

Eventually I spotted a pair of butterflies deep in the meadow foliage, mating.

They gradually moved higher on the sedge to which they were clinging, changing positions, taking turns being on top. They were intent on their goal.

Several times another butterfly, I’m guessing a male, tried to break up the happy couple.

They indicated their disinterest to him by flapping their wings.

When he persisted, they steadfastly ignored the intruder.

It was an hour and fifteen minutes between the first and last photos I took of this mating pair. They were already engaged when I encountered them, and they were still at it when I finally had to leave. (!)

They were not the only couple that managed to meet up. I did spot another example of splendor in the grass a bit further along the trail.

When I went back to check the Turtlehead where the initial caterpillar sighting took place, there were several females laying eggs (ovipositing). Looks like the Preserve will see another generation of Baltimore Checkerspots.

Resources

Cech, Rick; Tudor, Guy. Butterflies of the East Coast. 2005.

Glassberg, Jeffrey. Butterflies through Binoculars A Field Guide to Butterflies in the Boston-New York-Washington Region. 1993.

Scott, James A. The Butterflies of North America. 1986.

Butterflies of Massachusetts