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Long-term studies of the Chalcedon (Variable) checkerspot butterfly

Irene Brown (Independent)
Irene Brown reads a max/min thermometer in one of her Chalcedona study sites.


Irene’s long-term study of the chalcedon checkerspot butterfly (Euphydryas chalcedona) began in 1968, paralleling the, then, 8-year-long study of the Edith checkerspot butterfly (Euphydryas editha) by Paul Ehrlich and his colleagues, which continued until 1998 when E. editha was declared extinct at JRBP. See Ehrlich et al. on this site. 

In 1968, Irene chose 34 study sites, most in chaparral, contrasted to the 8 E. editha sites in serpentine grassland. All 34 were studied in 1968, 1976, and 1982. In 37 of the 40 flight seasons to 2007, she studied 7 to 9 sites, concentrating on two (one outside the fence). 

Using capture-mark-release-recapture, Irene records the beginning, end, and peak of the flight in the two main sites. Flight has started as early as 7 April and as late as 24 May. 

While most individuals stay where marked, some move to other sites. Population structure through 1977 was published in Brown and Ehrlich, Oecologia (Berl.) 47, 239-251, 1980. 

At JRBP, on the average, males are redder, and females blacker, but there is considerable overlap. The reason for this great variability is unknown, but detached wings dropped by birds, suggest that red may deter predation on females. See Bowers, Brown, and Wheye, Evolution, 39(1), 93-103, 1985.

Over the years, empty sites have been colonized, and populations have gone extinct. The main larval food of chalcedona inside JRBP, sticky monkeyflower (Mimulus aurantiacus), has spread – Chalcedona have followed. 

More Information on this continuing study will soon be available at Irene’s website. 

Left: After the photo was taken, this male Chalcedona was marked and released. Top: A female Chalcedona with little red on its dorsal wing surfaces. Bottom: The dorsal wing sufaces of this male Chalcedona are “checkered” with red.

Visible from Trail/Road

8 - Dam View

9 - Chaparral

10 - Teasel