Pine white butterflies find home in Tri-Cities

By Jacques Von Lunen, Tri-City HeraldSeptember 2, 2011 

Small, fragile transplants from Oregon seem to have made a permanent home in the Tri-Cities.

For the second summer in a row, pine white butterflies appeared in Tri-City conifers during the last week of August. At least one butterfly expert said their repeat showing was a significant biological event -- the settling of a new species in the area.

The pine white butterfly -- neophasia menapia menapia -- amazed friends of small, fluttering things when it showed up around here last summer. The small, bright-white insect with black-lined wings had not been seen here, said James Dillman of Richland.

He is the curator of the biological collection at Washington State University Tri-Cities.

Dillman and other lepidopterists -- butterfly researchers and collectors -- came up with a theory about the Pine Whites' arrival.

They figured the butterflies, which can only live in western pine tree forests, were sucked up into the air by thermal drafts in the Blue Mountains near Baker City, Ore., drifted northward on a stream of air and finally were dumped in the Tri-Cities.

They partially assumed this because the butterflies were seen in abundant numbers around Baker City just before they appeared here, Dillman said.

And almost as soon as people got used to seeing the pretty insects in their yards, they disappeared.

The pine whites don't live very long -- "one year from egg to egg," Dillman said.

Caterpillars hatch in the fall, eat pine needles -- and only pine needles -- until they burst their skin, spend the winter either as a caterpillar or a chrysalis and pop out as beautiful butterflies in August.

They mate, the females lay eggs and then "they all die," Dillman said.

But last week the winged creatures were back -- and this time they didn't fly in on an air stream.

It appears that the Tri-Cities has a homegrown colony of pine white butterflies now, Dillman said. And that's because humans have changed the landscape around here.

It's likely that the butterflies were carried here before at some point in history. But until people decorated backyards and parks with pine trees, no host plants for the butterflies existed in the Mid-Columbia, Dillman said.

Now there are plenty of pines and the butterflies seem to have established themselves here. "This time there something here for them," he said.

The butterflies only lay their eggs in pine trees, but they don't damage the tree. Even in areas where the butterflies are abundant, they are not considered a danger to pines. The caterpillars just don't eat enough of the trees' needles to do harm, he said.

While some butterfly species reportedly have been driven north by climate change, this is not the case with the pine white, Dillman said.

It's basically a historical coincidence of their drifting here and finding non-native pines planted in sagebrush country.

Dillman will speak about the butterflies' arrival at the next meeting of the Northwest Lepidopterists Association in Corvallis, Ore., this fall. He expects the news to create a stir among insect researchers.

To enjoy the butterflies up close, find a pine tree on a warm day in the next week or so, before the adults die off.

But don't catch any -- it's illegal.

-- Jacques Von Lunen: 582-1402; jvonlunen@tricityherald.com

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