| 1 | Atractus (ground snakes) |
Members: 141.
There are over 3900 snake species as of 2024, divided into 420 groups, or genera. A large handful have just one member, such as Calloselasma, which the lethal Malayan pitviper belongs to (Calloselasma rhodostoma). Then there’s genera which are truly enormous, with dozens of members. As of 2024, the largest snake genus worldwide is Atractus, AKA the American ground snakes.
Atractus is a group of burrowing snakes, whose members are almost uniformly shy and harmless. These snakes aren’t fully blind and fossorial like a blind snake, yet spend a significant portion of their time underground. There’s currently 141 species, and all but 5 live in South America, with those rare exceptions appearing in Panama, such as Atractus imperfectus.
New Atractus members are being discovered almost every year. Three were found in Ecuador in 2022 alone, including Atractus zgap, and another in 2023 in the Peruvian andes, dubbed Atractus paulus. Their shy ways mean that they easily avoid scientists, unlike the tiger ratsnake, which is always zooming around, or the boa constrictor, which is so huge that nobody could miss them.
Atractus members lurk quietly below everyone’s radar, where they eat a diet rich in earthworms, and sometimes insects. One consistent characteristic of Atractus is a small mouth, with a relatively narrow gape width.
One of the most common species is the broad-headed ground snake (Atractus latifrons), found across a huge swathe of Amazonian Brazil. Near the bustling city of São Paulo on the Atlantic coast, the most common member is Atractus pantostictus, AKA the fura-terra.
| 2 | Oligodon (kukri snakes) |
Members: 88.
A huge genus of southeast Asia and the Indian subcontinent, which typically measures 50-100cm. The 88 kukri snake members are united by several common characteristics. These include 1) an extremely mild venom which is incapable of killing human beings, but also 2) a pair of unusually sharp front fangs, which can easily draw blood with a slashing wound. The genus’ name originates from the lethal kukri daggers wielded by Nepalese Gurkha soldiers.
Rather than climbing trees and branches, kukri snakes mainly stick to the ground, although they sometimes climb low bushes in pursuit of prey. Two of the most common species are the banded kukri snake (India, Sri Lanka) and small-banded kukri snake (Thailand, Cambodia).
The kukri snakes cover an enormous amount of space in Asia. To the extreme west, you have the streaked kukri snake (Oligodon taeniolatus), which reaches Pakistan. At the opposite extreme, you have Forbe’s kukri snake, which lives on Indonesian islands not far from Australia, although no members reach Australia itself.
This snake genus thrives in warmth and humidity, avoiding chillier climates. To the northeast, kukri snakes just reach Shanghai, but fail to get near the Korean peninsular, let alone Japan.
Thailand lies at the epicentre of the kukri snake empire, with 21 species confirmed as of February 2024. The most recently discovered member was Oligodon churahensis, found in 2021, after scientists noticed an unusual-looking snake in an Instagram post, taken in India’s Himachal pradesh.
| 3 | Micrurus (coral snakes) |
Members: 82.
The largest genus of venomous snakes worldwide. The Agkistrodon genus of cottonmouths and copperheads numbers just 8, but the American coral snakes have swollen to 82, with the most recent addition being the Brazilian Micrurus boicora in 2020.
As a whole, the Micrurus genus is extremely lethal. The vast majority have neurotoxins, capable of paralysing muscles and triggering respiratory paralysis in a few measly milligrams. But due to their shy personalities, Micrurus coral snakes cause very few deaths overall, compared to cobras or lanceheads. The deadliest is probably the painted coral snake, found near São Paulo, but this still caused just 36 officially recorded bites from 1867 to 2014.
Coral snakes generally shun open spaces, with the vast majority favouring leafy forest floors, with a few exceptions like the aquatic coral snake. Some members can be impossible to distinguish for a layman. The USA has two Micrurus members, the eastern and Texas coral snakes, and the main difference is that the black ring edges slightly further up the Texas coral snake’s neck.
Micrurus is the genus of true coral snakes. This genus only inhabits the Americas, as others abroad belong to Calliophis, like the Malaysian blue coral snake, or Sinomicrurus, like MacLelland’s coral snake (Thailand). Primitive Micrurus fossils have been found in Nebraska dating back 16.0–13.6 million years.
| 4 | Lycodon (wolf snakes) |
Members: 73.
An enormous Asian group, which lacks any venom and kills its prey via constriction. The wolf snakes are flexible in their habitats, and usually stick to the ground, but inhabit forests, fields, beaches and farmyards alike. They often invade people’s homes, and bite fiercely if pressured. Some can even flip onto their backs and play dead.
The Lycodon wolf snakes cover a similar range to the kukri snakes overall: southeast Asia and the Indian subcontinent. Yet despite numbering 15 fewer species, they’re even more widespread. They have strong colonies in South Korea and Japan, in the form of the red-banded snake and oriental odd-toothed snake respectively.
Again, wolf snakes don’t quite reach Australia, with the closest species being the common wolf snake (Lycodon capunicus). The most extreme northwesterly species is the MacKinnon’s wolf snake, which inhabits the outskirts of Islamabad.
Of the 72 Lycodon members, the two most common are the Indian wolf snake, which controls India, Bangladesh and Sri Lanka, and the common wolf snake, which controls Thailand, Malaysia and Indonesia. The most recently discovered species was Lycodon cathaya from southern China, found in 2020.
| 5 | Tantilla (centipede snakes) |
Members: 68.
Another immensely shy group of snakes. The Tantilla genus is completely harmless to human beings, with no venom at all. While they’re not actually blind, they have similar habits to real blind snakes, such as lurking under leaf litter and soil, and mainly appearing post heavy rains.
As their name suggests, Tantilla snakes mainly feed on centipedes, with Atractus members occupying similar habitats, but preying on earthworms instead. The Tantilla genus has 7 members in the USA, including 4 in Texas and Arizona, and 1 in California. Another 2 are found in Florida, one of which is seriously endangered: the rim-crowned rock snake (Tantilla oolicta).
The most northerly Tantilla member is the plains black-headed snake, which reaches southeastern Wyoming. The most southerly is the black-headed snake (Tantilla melanocephala), which reaches Argentina. This species is easily the most common Tantilla overall, as it covers a huge swathe of Brazil.
Being so tiny, Tantilla members fall victim to many grisly fates, including being trapped in black widow webs, or swallowed by greedy false coral snakes. Across the Americas, there’s a wonderland of red, black and white Tantilla members, but all members are united by being shy and lurking under cover. This has the effect of keeping them hidden from researchers, meaning that like with Atractus, there’s almost certainly more Tantilla members out there, waiting to be discovered.
| 6 | Calamaria (reed snakes) |
Members: 66.
The Calamaria reed snake genus is less widespread than the kukri snakes or wolf snakes, but still manages to have 66 members. The northernmost is the northern reed snake, found near Shanghai, while the southernmost members live in Java, including Linne’s dwarf snake, which is extremely common near Jakarta.
The Calamaria genus is another completely harmless group. Its members are mainly nocturnal, lurking under shelter by day. The reed snakes are nearly all small burrowers, averaging at just 20-50cm long. They have very few gimmicks, but they might be the most consistently iridescent of the huge snake groups, with many members producing shimmering rainbow colours when exposed to bright light (see here).
Their ordinary colours aren’t too shabby either, with snowy white heads, vibrant lava stripes, blue bands, or sometimes a more boring consistent black. The Calamaria reed snakes are united by a tube-shaped head with little neck, round pupils, and no dangerous venom.
Very few species of this genus are well researched. Earthworms are confirmed prey in several species, including the white-bellied reed snake, pink-headed reed snake and variable reed snake. The latter two are some of the most widespread in the Calamaria genus.
Then there’s the collared reed snake, which is extremely abundant on Taiwan, and encountered by ordinary people much more often than most members. This is now our third massively common genus of shy burrowers; the king cobra should take note.
| 7 | Dipsas (snail-eaters) |
Members: 55.
Tied for 7th position, we have the largest snail-eating genus, Dipsas, which beats the Sibon snail-eaters of South America (22 members), as well as the Pareas snail-eaters of southeast Asia (30).
Dipsas members typically live in humid forests, from lowland rainforests to high altitude cloud forests, where they cling to branches 0.5-3 metres high, and keep a keen eye out for snails slithering along. The most common is probably Dipsas indica, the neotropical snail eater, which covers a large swathe of Brazil.
The most southerly member is the Bolivian snail eater, found in Argentina’s Buenos Aires province, while the closest to the USA is Gaige’s thirst snail-eater (southwest Mexico). Dipsas members can also appear in human-modified zones, resting on fences or even barbed wire.
Dipsas snail-eaters first discover a snail or slug by finding a mucous trail, inspecting and licking at the ground (or branch). They follow the trail, then attack the snail’s shell with their mouth, and wrap an entire body coil around the hard calcified armour. Then they use a specialised jaw to suck them free, with alternating mandibular retractions. Once swallowing is complete, they wipe their face on the ground to remove any slime.
That said, this diet isn’t uniform across the genus. A study from central Panama found that compared to the Sibon snail-eaters nearby, the local Dipsas snail-eaters also included a high proportion of earthworms.
Probably the most consistent feature in the Dipsas genus is their large round eyes. Their heads are larger than their necks, rather than a continuous tube like a coral snake. Dipsas members range from 30-110cm, and are often preyed on by coral snakes.
| 7 | Erythrolamprus (false coral snakes) |
Members: 55.
The Erythrolamprus genus occupies most of South America, plus Central America to as far north as Guatemala, with the most northerly member being Erythrolamprus bizona. This is an incredibly diverse group of snakes, to the extent that it seems odd that they’re all related.
While dubbed the false coral snakes, a good 50% don’t appear to mimic coral snakes, including the velvet swamp snake, which is often a bright green or blue. Even their diets are diverse: E. bizona in Central America feeds heavily on snakes, while the royal marsh snake (E. reginae) eats 95% amphibians, including frogs’ eggs. But one feature they do share is horizontal neck flattening, enlarging themselves sideways to appear larger, similarly to a cobra.
Likewise, the vast majority are moderately venomous. This is a rear-fanged group which must chew victims repeatedly, yet as a group, they have one of the most underestimated venoms. A bite from a yellow-bellied liophis (Erythrolamprus poecilogyrus) near Rio Grande in 2010 resulted in the victim having muscular pain up his entire arm for 5 days, which became worse when the muscles were flexed. Aesculapian false coral snakes can cause the victim’s entire arm to swell up.
Many of this group’s members originally belonged to Liophis, and a big chunk were handed to Erythrolamprus all at once when that genus was dissolved. Some are still called the liophis colloquially, like the yellow-bellied liophis, but officially belong to Erythrolamprus.
The most southerly member of this genus is the arrow ground snake (E. sagittifer), which plunges deep into Argentina, while the newest species is E. aenigma, discovered in the savannahs of northern Brazil in 2021.
| 9 | Geophis (Latin American earth snakes) |
Members: 54.
The Geophis genus covers the smallest geographical area of our list, but still numbers 54 independent species as of 2024, which are all non-venomous. Being small and secretive means that they require less land to roam about in compared to larger rattlesnakes. The vast majority are found in central America, plus Mexico, with a few spilling into Colombia, but none entering Brazil, or the USA to the north.
The Geophis species are a varied bunch. Some are shy burrowing snakes which eat slugs and earthworms (Hoffman’s earth snake), while others are committed snail suckers similarly to the Dipsas genus.
Some have small, beady black eyes, while others have large, bulbous eyes in order to scan branches for snails. Some have bulkier heads, while the Colombian earth snake’s head is narrow for digging into soft soils. Nevertheless, all Geophis members are harmless to humans, and can usually be picked up safely.
Some Geophis members are incredibly rare. Dunn’s earth snake of Nicaragua was only found once, in 1932, and never again since. The Colombian earth snake lives the furthest south, while Dugès’ earth snake lies closest to the US border, reaching northern Mexico. Overall, the most commonly encountered member by ordinary people is the terrestrial snail sucker (Geophis sartorii).
| 10 | Crotalus (rattlesnakes) |
Members: 53.
Among dangerously venomous snakes, the second most plentiful genus is the Crotalus genus of true rattlesnakes. That isn’t even including the Sistrurus genus, which contains massasaugas and pygmy rattlesnakes.
The USA has 20 rattlesnakes, and the dusty badlands of Mexico have about 30 more. The most southerly species is the South American rattlesnake (Crotalus durissus), which is found as far south as Argentina, and likely contains multiple hidden species.
In fact, the Crotalus rattlesnakes have the largest north to south distribution of any genus on this list. The most northerly is either the Pacific rattlesnake or prairie rattlesnake, which both inhabit southwest Canada.
Every single rattlesnake is dangerously venomous, though some are far milder than others. The majority are haemotoxic and cytotoxic, triggering swelling and spontaneous bleeding, or kidney failure in the largest species like the diamondbacks. A small subgroup are neurotoxic, causing paralysis – this includes the tiger, Mojave, and South American rattlesnakes.
The longest of the 53 is the eastern diamondback rattlesnake (record: 251.5cm), followed by the west diamondback (233.7cm), and the Mexican west coast rattlesnake (204.5cm). The vast majority prey on mammals and lizards, in varying ratios. Amphibians and fellow snakes are rare prey for rattlesnakes.