Pandora moths return to Sisters

Yes, those are Pandora moths flying about your porch lights at night. This isn't the first time they've been in Oregon's night skies, nor will it be the last.

Pandora moths are cyclic in appearance, taking between four and five years between outbreaks. The earliest record of their numbers dates back to 1894 when federal Indian agents noticed the Klamath people roasting Pandora caterpillars. Conversations with the Klamath elders indicated the caterpillars were a welcome food item - when they appeared, which wasn't that often.

The last significant outbreak in this area was in 1990 and '91 when adult moths were found from Crescent all the way to Sisters. The Bend area saw most of them, but they did not defoliate the pines as in times past.

And here the moths are with us again - noticeably flying about the lights of homes, barns and businesses. The adult moths, however, have no interest in eating, and even if they did, they couldn't, as they do not have a mouth. They're interested in one thing, and one thing only: mating.

Female moths are flying about releasing pheromones (scent) that are distinctive to their species, which the males, with their oversize, yellow antennae are quick to sense and recognize. Nature has dictated that they have only a very short time to get the job done; in about a week they'll all be dead.

Pandora moths are not found everywhere in the U.S.; it is the loose pumice soils that make this part of North America their desired habitat. The pine tree needles they devour go with the soils, making our area just right for this very specialized insect.

Their life cycle works something like this: around the end of June, the adult moths appear and dig their way out of the ground where they went from caterpillar to adult in the pupae stage. They mate and the females lay eggs, which hatch in August. Those larva satisfy their hunger by eating the needles of pines - and only pines.

They grow as they eat and at the point where they get too big for their outside skin, they grow a new layer beneath it and then burst the outer skin and the next instar (the term for growth of a caterpillar) emerges. After its seventh instar, the larvae (caterpillars) drop off the trees and bury themselves in the soft soils, where they will remain for a year (or, in some areas, two to four years), and eventually emerge as adult moths.

Hence their cyclic appearance.

On a big hatch year, the caterpillars' need to burrow underground in the right soils has caused costly problems for ODOT. During an outbreak in the 1970s, traffic on Highway 97 between Bend and Klamath Falls crushed millions of caterpillars crossing the highway, which became so slick that cars and trucks went sliding around smashing into one another. As a result, sanding trucks had to be employed to prevent more accidents.

Retired Sisters cross-country coach, Kris Kristovich recalls back in '91 when he and his 6-year-old grand daughter, Natasha, were attending a night baseball game in Vince Genna Stadium in Bend when the moths appeared in great numbers, making a real mess of things.

They are attracted to yard lights and other sources, so if you don't want them to lay eggs on your pines, turn off your lights; you'll save energy, not attract the moths, and save money at the same time.

Like other things in Nature, where everything is connected, there are "natural controls" for population build-ups. It's a "wilting virus" that puts the finish on expanding adult Pandora moth numbers. Also, during their population explosion, wasp and fly parasites lay eggs on and in the caterpillars, which also takes a great toll on the moths, while helping the wasps and flies to keep going.

Then there's our little screech owl look-a-like, the flammulated owl. They nest near Lava Top Butte south of Bend and in other pine forests with dead trees and woodpecker cavities. While most owls are rodent-eaters, the little flammulated is an insect-eater, with Pandora moths high on their diet.

You can kill them with chemicals, but why bother? The current outbreak is a small one and nearly over, so of little consequence to we humans.