Su­per bloom leads to a fuzzy, crawly in­va­sion of cater­pil­lars

The Tribune (SLO) - - Front Page - BY MONICA VAUGHAN

Hordes of cater­pil­lars in an Ar­royo Grande neigh­bor­hood have star­tled res­i­dents who can’t seem to walk down the street with­out crush­ing a crawler. And they may be com­ing your way soon.

They’re wig­gling up the sides of houses, march­ing across roads and chomp­ing leaves in res­i­dent’s gar­dens filled with weeds and hol­ly­hocks.

They’re likely the off­spring of painted lady but­ter­flies that hatched in the desert near the U.S.-Mex­ico bor­der and are flut­ter­ing for­ward in a mass mi­gra­tion to the Pa­cific North­west, Nor­man Smith, a re­tired en­to­mol­o­gist and a Mas­ter Gar­dener with San Luis Obispo Ag Ex­ten­sion, told The Tribune.

Res­i­dents say the quan­tity of cater­pil­lars is un­usual.

“We took a walk this morn­ing to walk our dog, and we just no­ticed there were hun­dreds of them walk­ing in the middle of the street, all of them head­ing in the same di­rec­tion. (They’re) all over houses in our neigh­bor­hood. It’s been a really neat thing to see,” said Sarah Smith, who walked with her chil­dren along Turquoise Street in the Hal­cyon neigh­bor­hood of Ar­royo Grande on Thurs­day to see the spec­ta­cle.

“This is our sec­ond walk to­day to see them,” Smith told The Tribune. The kids have “been su­per in­ter­ested.”

The cater­pil­lars won’t be there long. Soon, they’ll be­gin the week­long process of meta­mor­phos­ing into but­ter­flies, with bright-or­ange wings dec­o­rated with a white stripe and a row of five tiny black dots, as de­scribed by Univer­sity of Michi­gan’s Animal Diversity Web. Then, they’ll con­tinue the mi­gra­tion north.

It’s likely the big­gest boom in the pop­u­la­tion of painted lady but­ter­flies since 2005, UC Davis Bi­ol­ogy Pro­fes­sor Art Shapiro told Newsweek. That year in Sacra­mento, but­ter­flies were pass­ing in one’s field of vi­sion at a rate of three per sec­ond, ac­cord­ing to Shapiro’s web­site, which is ded­i­cated to track­ing but­ter­fly pop­u­la­tions across Cen­tral Cal­i­for­nia.

The flurry of but­ter­fly ac­tiv­ity this year was stim­u­lated by lots of rain that pro­duced boun­ti­ful crops of host plants in the desert

where painted but­ter­flies win­ter along the U.S.-Mex­ico bor­der, Shapiro said. Nearly a month ago, painted ladies swarmed South­ern Cal­i­for­nia, then Cen­tral Cal­i­for­nia.

In good years, they may mi­grate by the bil­lions, ac­cord­ing to Art Shapiro’s But­ter­fly Site.

Gar­den­ers shouldn’t be too con­cerned, Nor­man Smith said.

“I sug­gest that nothing be done about it as they will dis­ap­pear in a few days. Most of their host plants are weeds (like cheese weed), and so they are clean­ing that prob­lem up,” Smith said. “Adults that hatch out here will head on fur­ther north and do the same thing in the Bay Area or north of there.”


Emery Smith, 8, of Ar­royo Grande, picks up one of the hun­dreds of cater­pil­lars march­ing down Turquoise Street in Ar­royo Grande while walk­ing with her mom, Sarah. The swarm of painted lady but­ter­fly cater­pil­lars is not ex­pected to last long.

Above and left, many of the vo­ra­cious cater­pil­lars chow down on milk­weed plants.

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