Ceanothus silk moth

[ HYALOPHORA EURYALUS ]

Ranging from the coast to the Sierra Nevada crest, these huge, spectacular moths startle observers when they suddenly appear near nighttime lights for a few days each spring. Stimulated by longer days and warmer weather, large numbers of adults emerge from their elaborate silken cocoons at the same time, which maximizes their mating opportunities. Living only two to three days, the females stay hidden from predators and conserve their energy while announcing their presence to males by releasing powerful pheromones. Meanwhile, the males fly up to 20 miles in their short, frenetic lifetime as they zigzag frantically through wind, rain and cold, tracking down the females’ potent scent. The male’s oversize, feathery antennae act like a net that plucks single molecules of smell out of the air and allows it to find females against seemingly impossible odds.

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NATURAL HISTORY

By late spring, pale green caterpillars appear on ceanothus plants. Growing to 4 inches long, these caterpillars will spin a mile-long silken thread into an intricate, double-walled cocoon that houses the pupae over the summer and winter.

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KEY CHARACTERISTICS

The adult’s wings, which are 4 inches across, are primarily deep rust with white streaks and black eyespots.