Most caterpillars tend to rely upon camouflage or being as unpalatable as possible to protect themselves from predators, but the Eastern tiger swallowtail has a more unusual approach - it pretends to be a smelly snake.
The caterpillar of the Eastern tiger swallowtail, which is native to North America, has two green 'eyespots' on the top of its body that makes it look like a snake slithering between the leaves.
Incredibly, when disturbed the insect larvae shoots out two bright orange structures that look like the forked tongue of a snake.
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The Eastern tiger swallowtail pushes out a protrusion that looks like a snake's forked tongue (shown above)
And as if resembling a potentially dangerous reptile was not enough to put off hungry birds, the caterpillar has another weapon in its armory.
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Having bright colours and distinguishing features is a common way for insects to scare away predators like birds.
Often they help to lure them away from vital body parts or confuse them.
However, this only works on predators that hunt using sight while bats tend to be immune to such devices.
Now scientists have found that a moth has an unusual evolutionary adaptation that allows it to confuse the ultrasound used by bats.
The luna moth has two tails that extend for more than an inch beyond its body.
Scientists in the US showed that these appendages produce a confusing acoustic signature in the bats echolocation.
It makes the bats target the end of the tails rather than the moth itself.
Pushing out the orange tongue-like structure - known as an osmeterium - releases a powerful and smelly substance at the same time.
Now scientists have found evidence hidden in the genome of these strange butterflies that helps explain how they developed this in the first place.
The foul-smelling substance consists of chemicals called terpenes, which are created by enzymes in the caterpillar's body.
Most butterflies have just one or two of these enzymes, but the Eastern tiger swallowtail and its relatives, known as Papilio butterflies, appear to have many.
Writing in the journal Cell Reports, Dr Nick Grishin, a geneticist at University of Texas, said these butterflies exist appear to have broken off from the main branch of the butterfly evolutionary tree.
He said: 'The Papilio-specific FPPS enzymes form a clade in the evolutionary tree.
'We hypothesized that they could function in a pathway to synthesize predator-repelling terpenes secreted by the osmeterium, a Papilionidae-specific organ among butterflies.'
The researchers used a rapid and cheap DNA sequencing technique to assess the genome of the Eastern tiger swallowtail.
The Eastern tiger swallowtail caterpillar also has distinctive eyespots (pictured) that make it look like a snake
By looking like a green snake, like Opheodrys vernalis above, the caterpillar is able to frighten off predators
The geneticists also found that the butterflies appear to produce more molecules that are sensitive to green, blue and ultraviolet light.
This, they say, 'may indicate a more advanced colour perception'.
They also found that the butterflies have mutations in proteins that are responsible for the circadian rhythm - the internal clock that works in cells.
This, they say, might explain why Eastern tiger swallowtails mature quickly into adults and hatch from their chrysalises quickly compared to their cousins, the Canadian tiger swallowtails, which sleep through the winter.
The scientists also found the Eastern tiger swallowtails had high numbers of proteins involved in the detection of chemicals from their food.
Other species of Papilio butterfly, like the black swallowtail above, also use osmeterium to look like snakes
Dr Grishin and his colleagues added: 'They are also significantly enriched in proteins involved in the detection of stimuli (chemosensory ionotropic receptors), which may be related to the wide range of food plants they feed on.'
The butterfly's genome was found to be 376 million bases, or 'letters' of DNA, long. The human genome consists of 3.2 billion bases.
Dr Grishin said that with the technique they have developed, it may be possible to cheaply sequence the DNA of insects to identify them.
He said: 'With our protocols, the cost per new genome falls below $4,000, making insect sequencing projects feasible.
'We think the power of comparative genomics can be fully exploited only when there are thousands of genomes available.'
Despite the fearsome appearance of its caterpillar, the adult Eastern tiger swallowtail (above) is beautiful
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