The Washington expert drove 30,000+ miles, waded bogs, dissected rotting logs and combed fleas from a mountain beaver in his 14-year survey of Northwest insects.

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Merrill Peterson knows few people are as passionate about insects as he is.

But you don’t have to share the Western Washington University biologist’s obsession to appreciate his new guide to the bounty of beetles, spittlebugs, antlions, lacewings, stoneflies, treehoppers, katydids and other six-legged invertebrates that make their homes in the Pacific Northwest. All it takes is curiosity and a question: “What’s that bug?”

“Lots and lots of people wonder about the insects they find around them, whether they are hikers who run into something that piques their interest, or gardeners trying to figure out what’s eating their plants, or foresters or farmers or teachers,” said Peterson, who devoted 14 years to his quest to document and photograph the region’s insect life. “My real purpose was to try to help people connect with nature.”

Want to know more?

Gardening expert Ciscoe Morris will interview Merrill Peterson Aug. 25 on “Gardening with Ciscoe” on 97.3 KIRO FM radio, from noon to 1 p.m. Peterson also will appear at the Lake Hills Library in Bellevue at 2 p.m. Sept. 9.

Pacific Northwest Insects” is the first regional field guide that allows amateur bug-watchers to accurately identify a broad range of insects to the species level. It also contains enough detail to be useful to experts.

The common names alone paint a picture of staggering diversity and niches: Stigmatic snakefly; smooth take-caution beetle; glorious squash vine borer moth; mourning cloak butterfly; modest masked bee.

The project was a labor of love for Peterson, who drove more than 30,000 miles across Northern California, Oregon, Washington, Idaho, Montana and British Columbia in search of insects both abundant and rare. He waded through bogs looking for iridescent Beller’s ground beetles, and he dissected rotting fir logs in search of a type of roach that lives in family groups. It took him 10 years to find a minor ground mantis, an inch-long stick of a creature that zips through the desert scrub east of the Cascade Mountains.

“This was one of those projects that had me questioning my sanity many, many times,” Peterson said. “Pretty much every winter break, spring break and all summer would be [spent] working on the book.” Family vacations were regularly hijacked by insect-hunting expeditions.

Peterson’s most daunting encounter was with the world’s largest flea — or, rather, its host mammal. The half-inch-long bloodsuckers are up to five times bigger than a typical cat flea. They are called giant mountain beaver fleas because they live exclusively on mountain beavers — rodents that aren’t actually beavers and don’t live in the mountains. When attempts to collect fleas from a warren of burrows near Gig Harbor failed, Peterson’s only option was to capture one of the two-pound beasts, dodge its sharp claws and teeth, and run a flea comb through its fur.

“That was a new experience to me, and it was terrifying,” he said.

Luckily, the first mountain beaver that blundered into the apple-baited trap proved fairly docile — and yielded a single, giant flea.

(Peterson’s wife, science reporter Carol Kaesuk Yoon, wrote about the giant flea caper for The New York Times.)

The new guide doesn’t attempt to cram in all 30,000 insect species that live in the Pacific Northwest and that far outnumber all other animal species. Instead, it focuses on the approximately 1,200 insects that people most commonly notice, along with some more obscure species that are just, well, really cool.

Peterson puts ice crawlers in the latter category. Also known as ice-bugs or rock-crawlers, they look a little bit like earwigs but live high on mountain talus slopes and snow fields. At night, they creep out to feed on the bodies of other insects trapped in the snow. Exquisitely adapted to cold, ice crawlers wither and die from the heat of being held in a human hand.

Another group with a bizarre lifestyle are mantidflies. Adults look like a cross between a lacewing and a praying mantis, but start out as larvae that parasitize adult spiders and spider egg sacs, eating the young.

“Just knowing that there are odd things like that out there makes us appreciate our natural world more,” Peterson said.

Ice crawlers are so elusive that Peterson was never able to find one to photograph, despite repeated excursions in the North Cascades. He was luckier with many other insects, shooting about half the pictures in the book himself. When he got skunked, he turned to other experts or his students at WWU, whom he enticed with the promise of extra credit.

“I had lots of eyes and ears out on the ground,” he said.

All the photos are of live insects, some of which Peterson first chilled in a cooler to keep them still. He used an old-school Canon 10D DSLR camera and a 100mm macro lens with a flash mounted on its end for most of the shots. For the tiniest bugs, he switched to a 1x-5x macro lens.

In addition to its high-quality photos, the book goes beyond most traditional field guides by including rich summaries of life histories and habitats. To enable species-level identification, it describes insects in detail along with similar species with which they might be mistaken.

Many general insect guides are more frustrating than useful, said renowned butterfly expert Robert Michael Pyle, author of several field guides including the new “Butterflies of the Pacific Northwest.”

“You see a bug and you say: What in the world is this? And there’s nothing like it in the field guide,” he said. “There are so many kinds of insects — it’s 90 percent of animal life on Earth — that the diversity is overwhelming.”

By making smart choices on which insects to include, combined with clear photos and clear writing, Peterson avoids those pitfalls.

“Outside of Great Britain — which has fabulous guides and far fewer species — this is probably the best regional insect guide I’ve ever seen,” said Pyle.

Peterson’s infatuation with insects began when he was a boy in Seattle’s Laurelhurst neighborhood. When his family visited the zoo, he ignored the tigers and stared at bumblebees buzzing in the flowers. A visit to the butterfly collection at Denver’s natural history museum left him dazzled, and it inspired a lifelong fascination with Lepidoptera, the order that includes butterflies and moths. Pyle, founder of the Xerces Society for Invertebrate Conservation, was one of Peterson’s early mentors.

Peterson is still stalking moths. Work on the new insect guide was temporarily sidetracked by a project to develop the first comprehensive, online guide to the region’s moths.

One of the more surprising finds reported in the book was a lovely little moth never described before in the Northwest. Peterson found it in his backyard, and it turned out to be a European species that’s threatened in its native habitat. His yard also yielded the first documented sighting west of the Rocky Mountains of an invasive sawfly species that feeds on spruce trees.

“I’m sure that doesn’t mean it showed up in my yard first,” he said. “It’s just an indication of how many things are out there to be discovered if you start looking.”