Reptiles
Scarlet Kingsnake
Lampropeltis elapsoides · also called scarlet kingsnake, scarlet milk snake
The scarlet kingsnake is a small, harmless snake that has borrowed a deadly reputation. Ringed in the same red, black, and yellow as the venomous coral snake it lives alongside, it is left alone by predators that have learned those colours mean trouble — a piece of protective mimicry precise enough to fool people too.
Overview
Scarlet kingsnakes live in the southeastern United States, in pine flatwoods, sandhills, hardwood forest, and gardens. They are small (usually under 50 cm), slender, and among the most secretive North American snakes, spending nearly all their time under pine bark, in rotting logs and stumps, and underground, hunting skinks and other lizards, which they kill by constriction. They have no venom.
Mimicking the coral snake
The kingsnake’s red, black, and yellow banding closely copies the venomous eastern coral snake — an example of Batesian mimicry, in which a harmless species resembles a dangerous one and is avoided by predators that have learned to fear the model. Where coral snakes are absent, kingsnake banding tends to be less precise, showing the mimicry is maintained by the model’s presence.
Telling them apart
In the US, the rule is which colours touch: on the coral snake, red touches yellow; on the scarlet kingsnake, red touches black, and the snout is red. The rhyme “red touches yellow, kill a fellow; red touches black, friend of Jack” captures it — but it fails outside the US and can be broken by odd individuals, so the safe policy is to never handle any small banded snake.
Not quite a milk snake
Long treated as a subspecies of the eastern milk snake, it is now usually recognised as its own species. Like other kingsnakes it eats other snakes and is immune to pit viper venom.
Status
The scarlet kingsnake is Least Concern and widespread, though so secretive it is easily overlooked.
Scarlet Kingsnake: common questions
How do you tell a scarlet kingsnake from a coral snake?
In the United States, look at which colours touch. On the venomous eastern coral snake, the red bands touch the yellow bands. On the harmless scarlet kingsnake, the red bands touch the black bands, and its snout is red rather than black. The mnemonic "red touches yellow, kill a fellow; red touches black, friend of Jack" (or "venom lack") captures this. There are important caveats — the rhyme is not reliable outside the US, where coral snakes have different patterns, and an abnormally patterned individual of either species could break the rule — so the safe policy anywhere is simply not to handle any small banded snake and to leave it alone.
What is Batesian mimicry?
It is when a harmless species evolves to resemble a genuinely dangerous or unpalatable one, so that predators which have learned to avoid the dangerous model also avoid the mimic. It is named after the naturalist Henry Walter Bates, who described it in Amazonian butterflies. The scarlet kingsnake is a classic vertebrate example — it gains protection from birds and mammals that have learned, from bad experiences or instinct, to steer clear of coral-snake colours, even though the kingsnake itself is completely harmless. The mimicry works best where the model is present and moderately common; studies show that kingsnake populations far from any coral snakes tend to have less precise banding.
Is the scarlet kingsnake a "milk snake"?
It was long treated as a subspecies of the eastern milk snake (Lampropeltis triangulum) and is still sometimes called the scarlet milk snake, but genetic work has led most authorities to recognise it as its own species, Lampropeltis elapsoides. It belongs to the same group — the milk snakes and kingsnakes — which are constrictors known for eating other snakes, including venomous ones, and for being immune to pit viper venom. The "milk snake" name comes from an old and false folk belief that these snakes milk cows; they are found in barns because that is where the rodents are.
Why is it so rarely seen?
The scarlet kingsnake is small, slender, and intensely secretive. It spends the great majority of its life hidden — beneath the bark of standing dead pines, inside rotting logs and stumps, under debris, and in underground burrows — hunting the skinks and lizards that shelter in the same places. It is most often found by people peeling bark off dead pine trees or turning cover objects, and it becomes briefly more visible on warm, humid nights and after heavy rain. Its bright colours, so striking in a photo, are actually rarely on display in the wild.