Thousands of people, including experts, had seen an animal without realizing it was a new species, but a close look at its genitals finally revealed the truth.

Everyone thought the butterfly, found living at high altitudes in northern Israel, was a Persian fritillary but the insect is actually a different species that looks similar, according to a study in the journal Comparative Cytogenetics. “Analysis of their male genitalia revealed them to be clearly different” and a DNA analysis backed that up.

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The butterfly is indeed a fritillary, a type that often has orange wings with black spots, but the DNA shows it to be distinct from the others in its family. It is a hybrid of butterflies in the Melitaea genus — a rare kind of butterfly to find — that has been around for a while. The study called it “old, well-established.”

“This population is ancient,” the author wrote. “It was estimated to originate 1–1.6 million years ago” and shares a common ancestor in its evolution with the butterfly it was previously mistaken for, M. persea.

The newly discovered species, which flies over the ski slopes at the snowy Mount Hermon resort, is being called Melitaea acentria. It is the first new butterfly species found in Israel in more than 100 years.

“To me, it was a surprise that no one had already discovered it,” insect scientist Vladimir Lukhtanov, from the Zoological Institute in St. Petersburg, said in a report from the journal’s publisher, Pensoft Publishers. “The species is probably one of a handful of butterflies known to have arisen through hybridisation between two other species in the past.”

Although there are hybrids of other living creatures, Lukhtanov said, “scientists have only recently realized it might also be present in butterflies.”

The study described the newly discovered butterfly species as having a rounded forward wing between 16 and 20 millimeters that on its upperside is orange-red with black spots and a black border. The underside is largely the same on the forewing but the hindwing is mostly yellowish-white.

“The wing markings are small and delicate,” according to the description of the male butterflies. But females are a little different: The main color of their upperside “is slightly lighter and black markings heavier than in males.”

There are thousands of butterfly species throughout the world and they are more than just something nice or colorful to look at. Although bees are more well-known for pollinating flowers, butterflies also do some of that work, even though they don’t lift as much weight as the bees. They are also a crucial link in the food chain, as birds, wasps and other animals feed on them.

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