Adult Island Marble Butterfly on a field mustard plant, May 2023 | Marianne Tynan

Late in May, Kathleen Lewis, SJPT Special Projects Director, discovered 35 Island Marble Butterfly eggs and two second-stage larvae in the plot at Frazer Homestead Preserve on San Juan Island.

Island Marble Butterfly in a field of mustard | Marianne Tynan

Even though they’re still in early stages, this is a doubling of occupants from last year, and the highest number of detections we’ve had at Frazer since we started the Island Marble Butterfly Project there. This marks four years out of five that the Preservation Trust has observed IMB occupation there, so we continue to remain hopeful that this will be a regularly occupied site.

We’ve also had two confirmed adult butterfly sightings so far this year in the patch. We didn’t see any adults flitting around last year (though clearly one visited, since there were eggs). Now that we know where the butterflies and their offspring are, we’re cautiously continuing invasive plant control in other areas of the habitat plot, as well as keeping extra watchful eyes.

SJPT and our partners will continue to monitor the habitat patches to collect more observations on the progress of this generation of IMB. Thanks to the San Juan County Conservation Land Bank in particular for their continued partnership on this property and this project.