“Raising 200 babies will be a task in itself!”

Kimberly Castaldo wrote that in an email earlier this week. She was referring to the 208 monarch butterfly caterpillars and eggs collected at the Rockwood Hall section of Rockefeller State Park Preserve on Monday, Aug. 24.

Located north of Phelps Hospital and the Kendal on Hudson retirement community, Rockwood Hall boasts panoramic views of the Tappan Zee and Hook Mountain. 

Castaldo works as the land steward coordinator for the 1,771-acre preserve. She was joined by Will Starkey, a summer intern and soon-to-be student at the University of Vermont, where he will study wildlife and fisheries biology. His father, David, owns Tomatillo restaurant in Dobbs Ferry.

Castaldo and Starkey spent Monday, Tuesday, and Wednesday at Rockwood Hall, which used to be the site of a 204-room mansion built by William Rockefeller. For hours, they checked leaf after leaf, on plant after plant, for the microscopic eggs and often microscopic caterpillars. On Monday, a mature caterpillar (pictured above) was the highlight.

Monarchs only lay their eggs on milkweed, often on the underside of newer, tender leaves. The eggs resemble the white sap that bubbles from the plant, hence the reason for its name.

The 208 caterpillars and eggs were moved to a new butterfly enclosure near the preserve’s visitor center, inside the main entrance off of Route 117. Castaldo and dozens of volunteer ambassadors raise the monarchs and then release the butterflies at the preserve.

Preserve staff planned to mow the meadows at Rockwood Hall at the end of this week in an effort to curb invasive plants and to promote native species. The caterpillars and eggs collected on Tuesday and Wednesday were moved to areas that would not be mowed.

Earlier this summer, far fewer monarch eggs were counted at Rockwood Hall. None were found in June, 10 in July, and 13 at the beginning of August, as was reported in this column three weeks ago. Castaldo suspected that dry weather was the reason for the low numbers.

Every spring, generations of monarchs migrate north from Mexico to the eastern United States, and then return to Mexico before winter. Thanks to Castaldo, Starkey, and the preserve’s ambassadors, hundreds of monarchs will continue that pilgrimage.

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