Hungry caterpillar vs. Mount St. Helens



A tiny insect has played a big role in delaying the recovery of the ecosystem around Mount St. Helens since the volcano's eruption shook Washington and Oregon in 1980.

When the volcano erupted, it heated everything around to 1,000 degrees Fahrenheit and left a gray, moonlike landscape - devoid of wildlife - for 40 square miles.

The first plants returned within a year.

But a University of Maryland ecologist has found that a caterpillar is slowing nature's recovery by eating up the lupine bush, a low-growing, short-lived perennial plant that is usually among the first to re-colonize denuded landscapes. The caterpillar of the Filatima moth ties lupine leaves in silken masses and feeds on them, reducing the number of seeds and the rate that lupines are spreading, says researcher William Fagan.

Fagan and John Bishop, a researcher from Washington State University, began looking at the processes influencing the ecological recovery at Mount St. Helens about 10 years ago.

Most previous studies de-emphasized the role of insects in how quickly plants and other species re-colonize an area. But Fagan says the study shows plant-eating insects have a major impact.

The study, in the December issue of the American Naturalist, should also help scientists understand the role insects play in the recovery of habitats destroyed by forest fires, hurricanes, floods and other disasters, the researchers say.

The analysis shows lupine expansion is one-fourth as fast as it would be without the caterpillars.

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