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Originally published July 28, 2014 at 7:57 PM | Page modified July 29, 2014 at 10:34 AM

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A giant that’s still hard to spot: the world’s largest flea

The world’s largest flea, which is at home in the Pacific Northwest, is an awe-inspiring colossus that can reach nearly half an inch, its head alone the size of a cat flea or dog flea.


The New York Times

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Well, so much for my aspirations to get a pet beaver... MORE

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GIG HARBOR — In the Pacific Northwest, we live among behemoths — snowcapped volcanoes, towering trees, great splashing salmon and lattes as big as a child’s head. Yet one of the region’s undeniably superlative titans has slipped beneath everyone’s radar.

The land of Bigfoot and Starbucks is also home to the world’s largest flea. The flea, Hystrichopsylla schefferi, is an awe-inspiring colossus that can reach nearly half an inch, its head alone the size of a cat flea or dog flea. Until last month, however, there existed not a single confirmed photograph of a live member of the species.

Never mind that with ubiquitous digital cameras, the documentation of life has exploded, or the fact that the flea lives on the mountain beaver, Aplodontia rufa, a species so abundant in forests and gardens around here that it is considered a pest.

Still, for long years, this gaping hole in the world’s biological record remained of little consequence to pretty much everyone. Then my husband, Merrill Peterson, a biologist and curator of the insect collection at Western Washington University in Bellingham, began writing a photographic field guide to the insects of the Pacific Northwest (to be published in 2015 by the Seattle Audubon Society). Fleas are insects, and Merrill became obsessed with getting a photograph of the world’s largest for his book.

He found drawings and dead specimens of the flea, which has been known to scientists since 1919, but no photographs of a live one. Photographs labeled “Hystrichopsylla schefferi” can be found online, but the specimens shown are small enough to possibly be a different flea species. To authenticate them as members of the biggest species would have required examination of minute details like the presence or absence of tiny hairs at the base of the hind legs.

So how to find the world’s largest flea? First, find mountain beavers. Though ubiquitous, they are not easily pinpointed, it turns out. They make their presence felt during the wee hours, when they emerge from their burrows to eat, especially ferns and seedlings like newly planted firs. But they are so secretive — spending most of their lives digging long, winding tunnels — that people often don’t know it’s mountain beavers that have done the damage.

Luck came in the form of a good friend and biologist, Peter Wimberger, whose colleague Bob Peaslee, the science support engineer at the University of Puget Sound, lives on land in Gig Harbor overlooking the Sound. Its steep hillside is plagued with mountain beavers.

The original plan did not involve any contact with a mountain beaver. Unlike many parasites, this flea spends time off its host and can sometimes be found in the nest material. Merrill and Peter set out with a group of undergraduates digging out mountain-beaver tunnels on a nearly vertical bank. But many hours and many shovelfuls later, there was no sign of nest or flea.

Resigned to having to get a flea directly off a mountain beaver, Merrill sought the advice of Wendy Arjo, a wildlife biologist with Ageiss, an environmental consulting firm based in Evergreen, Colo., who has worked often with mountain beavers.

It’s simple, she said. Trap a mountain beaver (perfectly legal). Coax it into a burlap bag, face first. Hold it just behind the jawline — not too far up, or you will be bitten; not too far back or it will get loose and then you will be bitten. Peel open the bag to reveal the hind end. Comb for fleas. Easy peasy!

Mountain beavers move easily across the line that divides cuddly and horrifying, depending on whether you find them gently grazing among ferns or coming at you with bared teeth and claws.

Much to our surprise, the mountain beaver that we trapped ambled agreeably from the trap into the bag. Merrill, having donned his newly purchased gloves, closed the sack and observed the slow-moving lump, trying without success to figure out which part was the head. He made rapid, tentative grabs, sometimes getting hold of something, then losing his grip and trying to get his hand quickly away. Was that the tail? Where were the claws? Those teeth?

Eventually, Merrill got his hand behind the mountain beaver’s head and kept hold. He peeled back the bag to reveal its adorably fuzzy gray bottom, covered in short and soft hairs. He began to comb. No flea. He combed a bit more. No flea.

At which point the mountain beaver got loose. Amid my screaming, somehow Merrill got the bag reclosed with the mountain beaver resting inside.

He then asked me to cut away as much of the bag as possible so he could comb more of the mountain beaver. And though burlap was all that stood between us and teeth and claw, I cut.

He combed the underside of the beast. Something brown tumbled down. Merrill began shouting, “Flea! Big flea!”

Next came the aspirator — a plastic vial stoppered by a rubber plug through which were threaded two thin metal tubes, with small rubber hoses attached. The end of one hose in my mouth, I held the tip of the other over the flea, where it lay amid mountain beaver fur.

After several tries, the flea was in the vial.

There it was, a surprisingly sluggish creature — the world’s largest flea, at a definitive 8 millimeters, almost one-third of an inch — tumbling about the vial.

We thanked and released the mountain beaver, who despite its ordeal, we could comfort ourselves in knowing, was living with one less bloodsucking parasite.

When we got home, I looked, for the first time, at what the authorities had to say about mountain beavers. The Washington Department of Fish and Wildlife captured the consensus, emphatically warning against ever handling these animals, which give “a very bad bite.” Did I mention that you should not try this at home?

Merrill now has scores of photographs of the world’s largest flea; it will be preserved at the insect collection he oversees at Western Washington University.

We may never know why this patch of earth and the mountain beaver have been graced with the world’s biggest flea, the oxymoron to end all oxymorons. But we can take pleasure in knowing that this beast, this entomological paparazzi’s dream, our own superlative and wild champion, moves in mystery, always beneath our feet — and soon in a book, which may be where it best remains.



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