SALMON, Idaho (Reuters) - Sleepy Hollow has its headless horseman and now Montana has a headless ladybug.

The newly discovered insect tucks its head into its throat - making it not only a new species but an entirely new genus, or larger classification of plants and animals.

Ross Winton captured the insect in 2009 in traps he set in a sand dune while an entomology graduate student at Montana State University. Winton, now a wildlife technician in Idaho, at first thought he had parts of an ant but then discovered the bug can hide its head, much like a turtle ducking into its shell.

Winton sent his discovery to scientists in Australia working on this group of insects and the headless ladybug was formally described in a recent issue of the peer-reviewed journal Systemic Entomology.

Just two specimens of the tan, pinhead-sized ladybugs, also known as ladybird beetles, have ever been collected, a male in Montana and a female in Idaho, scientists said, making it the rarest species in the United States.

Entomologists historically used males to describe beetle species so the credit for the new discovery went to Winton.

However, the new species - Allenius iviei - was named after his former professor and Montana State University entomologist Michael Ivie.

The insect, with the proposed common name "Winton's Ladybird Beetle," may prey on aphids and other plant pests.

Ivie said it was rare to discover a new beetle in the United States and rarer still to uncover a completely new genus. The discovery is no small accomplishment considering the bug is the size and color of a grain of sand, he added.

He said it was unclear why the beetle slips its head into a tube in its midsection.

"It's a whole new kind of ladybug. Whatever this does, it is very specialized. It's quite the exciting little beast," Ivie said.