When you see a long, spindly creepy crawly on the ground, there are only two things it can be: a snake or a centipede. Although they look alike at first glance, there are a few physical and behavioral differences between them.
Both black-headed snakes and centipedes can be venomous and deliver a painful but non-fatal bite to humans. They’re also nocturnal and fossorial or semi-fossorial animals. However, they have different habitats and diets. Some black-headed snake species also have different-colored bodies.
In this article, I’ll talk about the black-headed snakes and centipedes that you can find in the US, their subspecies, habitat, and feeding habits. Read on to learn more about how to properly tell them apart.
Black-Headed Snake vs. Centipede
Here is a summary of the differences between black-headed snakes and centipedes commonly found in the US:
| Species | Black-headed snake | Centipede |
| Class | Reptilia | Chilopoda |
| Subspecies | Mexican Black-headed Snake, Tantilla atriceps Southeastern Crowned Snake, Tantilla coronata Trans-Pecos Black-headed Snake, Tantilla cucullata Flat-headed Snake, Tantilla gracilis Smith’s Black-headed Snake, Tantilla hobartsmithi Plains Black-headed Snake, Tantilla nigriceps Rim Rock Crowned Snake, Tantilla oolitica Western Black-headed Snake, Tantilla planiceps Florida Crowned Snake, Tantilla relicta Chihuahuan Black-headed Snake, Tantilla wilcoxi Yaqui Black-headed Snake, Tantilla yaquia | The Scolopendrid Centipede, Scolopendromorpha The Cryptopid Centipede, Theatops californiensis The Bark Centipede, Hemiscolopendra The Stone Centipede, Lithobius forficatus House Centipede, Scutigera coleoptrata |
| Venomous | Yes, but not fatal to humans | Yes, but not fatal to humans |
| Envenomation method | Bite | Pinch, bite |
| Habitat | Wooded areas Desert areas Grasslands | They can be found everywhere, from deserts to swamps, but prefer a damp environment |
| Diet | Centipedes Scorpions Spiders Insects | Crickets Cockroaches Spiders Bedbugs Moths Earthworms Other centipedes |
Let’s take a closer look at the black-headed snakes and centipedes:
Species
The Black-Headed Snake
The black-headed snakes are reptiles from the Colubridae family. They are more commonly known as centipede, blackhead, or flathead snakes.
Although they have the characteristic black heads, members of this family can have bodies that vary in color, ranging from different shades of brown to red and black. The black-bodied ones are often mistaken for centipedes at first glance.
The Centipede
Centipedes are predators from the Chilopoda class. They have segmented bodies with a pair of legs per segment. Although their name literally means “one hundred feet,” the number of legs a centipede has can range from only 32 to as many as 382.
Size
The Black-Headed Snake
These snakes are quite small and are usually between 7 and 15 inches (18 and 38 cm) in size. The smallest ones among them are:
- The Smith’s Black-headed snake is between 4.5 to 15 inches (11.4 to 38 cm).
- The Flat-headed snake is 7 to 8 inches (18 to 20 cm) in size.
- Florida Crowned snakes range from 7 to 9 inches (18 to 23 cm).
The largest is the Trans-Pecos Black-headed snake, the longest recorded specimen being 18 inches (46 cm).
The Centipede
The centipedes you can find in the US usually vary in size between half an inch and 11.8 inches (1.25 and 30 cm).
The smallest one is Hoffman’s dwarf centipede (Nannarrup hoffmani), which is only 0.4 inches (10 mm) long. It holds a place in the Guinness Book of Records as the smallest centipede in the world.
The biggest centipede in the US is the Texas redheaded centipede, also known as the giant desert centipede or the giant Sonoran centipede. It can grow up to 9 inches (23 cm) in length.
Venom
Both the black-headed snake and centipede are venomous, but there are differences.
The Black-Headed Snake
These snakes are mildly venomous, making them a danger to their prey but not to humans. Moreover, they are not aggressive and won’t bite, even in self-defense. Although their bites don’t really affect humans, in the rare chance you do get bitten, it’s always best to see a medical professional because of the risk of infection.
The Centipede
House centipedes, stone and bark centipedes, Scolopendrid, and Cryptopid centipedes are all venomous. They don’t pose any real danger to humans, but their venom is quite potent and unpleasant.
When threatened or mishandled, they inject their venom under the skin with forcipules. Small species of centipedes can only cause irritating, localized pain with their bite, but large centipedes like the Texas redheaded centipede can cause an extremely painful bite with swelling, itching, and burning.
Sometimes the bite can cause headaches and nausea. In worse cases, it can result in a rise in blood pressure and swelling of lymph nodes.
Habitat
The Black-Headed Snake
These snakes are found throughout the United States. Some prefer deserts and grasslands, while some prefer forests and prairies. Almost all of them like moist soil (under rocks, leaves, or logs), and many spend a lot of their time underground, making them fossorial.
The Centipede
Centipedes can be found in all of the US. In our homes, they prefer dark and wet places, while in nature, they live in all habitats, from deserts to the seaside. They like high moisture areas, like rotting stumps, stones, and decaying leaves. Like snakes, they are also fossorial or semi-fossorial.
Diet
The Black-Headed Snake
Black-headed snakes eat insect larvae, slugs, earthworms, crickets, roaches, spiders, and caterpillars, but their primary food source is centipedes.
Although centipedes can grow quite big, black-headed snakes can easily subdue them and then eat them by injecting additional venom into the centipede’s body while chewing them.
However, accidents still happen. For instance, in February of 2022, a man visiting John Pennekamp Coral Reef State Park stumbled onto a bizarre sight: a dead Rim Rock crowned snake, the rarest American snake with only 26 known individuals, choked on a centipede.
The Centipede
Centipedes are strictly carnivores — they consume only meat. They eat fishmoths, bedbugs, spiders, moths, roaches, and crickets.
Centipedes possess fantastic speed, which they use to hunt their prey. After catching their meal, they paralyze it with venom.
They do, however, also eat dead animals. Some species are also cannibals. It’s not unusual for them to eat other centipedes, with mothers sometimes even eating their eggs.
Just to show that what goes around comes around, there are some centipedes that are known to eat snakes, like in the case of the Texas redheaded centipede in the US. This isn’t such an uncommon phenomenon around the world, and there is a lot of video evidence to support this claim.
Here is YouTube video of a Scolopendra centipede, commonly found in the Southwest United States, eating its natural predator — a snake:
Final Thoughts
Despite the visual similarity and tendency to live in similar conditions, there aren’t many common features between centipedes and black-headed snakes.
Although both critters look like something you might not want to encounter, it’s important to remember they are both essential links balancing the ecosystem. Centipedes are excellent house cleaners as they kill pests in our homes. On the other hand, snakes keep the population of insects in check.
And if you’re a brave soul who likes exotic animals, black snakes and centipedes make fine pets with proper care and handling.