Sacramento Valley’s Butterflies Hard-Hit by 1998 Cold Snap

Butterfly populations in the Sacramento Valley and nearby foothills hit a 28-year low in 1999, according to UC Davis entomologist Arthur Shapiro. But the problem is not human intervention, he added. The villain was a freeze during Christmas week of 1998, which reduced the survival of overwintering eggs, caterpillars, pupae and adults, and a cool spring and summer, he said Tuesday.

Of the region’s 55 resident species, he said, 14 were largely or completely missing during his biweekly surveys. Some of those most affected were orange sulfur butterflies, fiery and field skippers, pygmy blue butterflies and the buckeye, one of the most common butterflies in gardens and urban vacant lots. Also missing were the popular black-and-orange monarch butterflies.

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--Compiled by Times medical writer Thomas H. Maugh II