FRIENDS OF EDGEWOOD NATURAL PRESERVE
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FRIENDS OF EDGEWOOD NATURAL PRESERVE
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LIFE CYCLE OF AN ISLAND NYMPH: BAY CHECKERSPOT BUTTERFLY By Susan Sommers Living a sun-loving life in the islands of serpentine grasslands in Edgewood and Jasper Ridge Biological Preserve is the Bay Checkerspot Butterfly, Euphydryas editha bayensis. Its family, Nymphalidae, named after the goddess of waters, meadows, and forests, is known as the "brush-footed" butterfly family and is the largest, most varied true butterfly family among the few fossil butterflies identified. "Brush-footed" refers to the family characteristic feature on both sexes of the forelegs being reduced to mere stumps enclosed by the long hairy body scales. These butterflies live their entire lives in the serpentine grasslands on a select few plants. A fertilized female lays her eggs at the base of the California Plantain (Plantain erecta) in clusters. Upon emerging, the larvae, fuzzless caterpillars, begin eating the plantain and spin a communal web to protect themselves from predators. When alarmed, they all raise their tail end in unison as a defense response. Insects must shed their skin in order to grow, and these stages are called instars for butterfly larvae. Quickly the young larvae eat themselves out of house and home, thus by the time they have reached their first or second instar they move away in search of food. In order to survive the hot, dry Mediterranean summer that occurs in these habits, the larvae must reach their mid-third instar before the plantain dries. Some larvae will use the Purple Owl’s Clover (Orthocarpus densiflorus) for food as the plantain disappears. During the summer, the larvae "rest" as they enter into a diapause period; they do not eat in this state. With the advent of the autumn rains, the plantain sprouts, and the larvae again become active diners on the tender sprouts. Bay Checkerspot larvae spend the winter in pupae, a non-hairy cocoon. With the warmth of spring, they emerge as adult butterflies, drinking the nectar from the Hog Fennel (Lomatium), Tidy Tips, Goldfields, and Linanthus. The males are out first and scout the habitat site for the females who emerge later but with some of their eggs already ripe. With each mating, a chemical reaction creates a plug in the female preventing additional mating until those eggs are laid. Selecting a California Plantain, a fertilized female lays her eggs at the base. And, having done so, she flies on, leaving a new generation to continue the cycle of life in the serpentine grassland islands. |
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