BURLINGTON, Vt. (AP) — Streaked and gooey-looking, the caterpillar of North America's largest butterfly looked for all the world like a big bird dropping.

"Beauty is in the eye of the beholder, as you well know," advised Margaret Skinner, an insect researcher at University of Vermont Extension.

Off-putting larval camouflage serves the giant swallowtail butterfly well, she continued, and so does the East Coast's steadily warming climate — which over the decades has extended the insect's Florida-to-Mid-Atlantic migratory range north.

Slimy Papilio cresphontes larvae also appear willing to fight for added territory.

Historically, giant swallowtails have only intermittently ventured into northern New England, probably on the wings of extended warm spells, according to Kent McFarland of the Vermont Center for Ecostudies.

The region has seen a steady influx in the past decade.

Skinner spotted four caterpillars Tuesday afternoon at the UVM horticultural farm, feeding on low-growing hoptree (or prickly-ash) — a plant in the citrus family.

She nudged the rear-end of largest leaf-top blob, which responded with an elaborate gross-out.

The bird-dung lookalike morphed into what looked like a snake's head. From that creature's "mouth" darted a red, forked protuberance that flickered with menace.

Skinner oozed enthusiasm. The finger-sized creature reared back and struck harmlessly at her thumb.

"It thinks that we're a predator and it's trying to scare us away," she explained.

A big black ant — a more plausible predator — scrambled up the leaf to investigate. The caterpillar repeated its feisty performance, and the ant backed off.

Other insectivores lurked in the hoptree: a daddy-long-legs, a stink-bug and a lady-bug. Birds patrolled overhead. White stains on several leaves, close by the fake droppings, were the genuine article.

Vermonters, for the most part, leave the ungainly larvae alone, Skinner said, but in Florida, citrus-munching giant swallowtail caterpillars (and by default, the egg-laying adults) are considered serious agricultural pests.

"We don't really have that problem," Skinner said. "Not a lot of citrus plantations around here — not yet."

Track sightings of the giant swallowtail (and other butterflies) at the citizen-science site e-butterfly.org.

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Online: https://bfpne.ws/2wB27Bk

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Information from: The Burlington Free Press, http://www.burlingtonfreepress.com