Top 10 Deadliest Spiders – By Deadliness Score

Deadliest Spiders

Deadliest Spiders

Often feared, but surprisingly, only a few spiders are truly dangerous to humans.. and human fatalities are quite rare.  It would be too easy to just score the Top 10 Deadliest Spiders based on a spiders’ venom..  so we CritterScore it – a weighted system out of 100 points to obtain the Dealiness Score!

Fun Spider Facts

Did you know…?

  • Hydraulic Legs: Spiders dont use muscles to extend their legs but instead pump fluid into them like a hydraulic system
  • Silk Strength: Weight for weight spider silk is stronger than steel and tougher than kevlar while remaining flexible
  • Dry Bites: Many spiders deliver bites without venom as a warning to save their toxic resources for actual prey
  • Vibration Sensors: Tiny hairs on a spiders legs can detect the frequency of prey caught in a web or footsteps on the ground
  • Open Circulatory System: Spiders do not have veins; their blood called hemolymph sloshes freely around their internal organs

How the Deadliness Score Works

The Deadliness Score ensures that the ranking reflects overall danger to humans, not just raw venom strength.  Here’s how we CritterScore them to obtain the Dealiness Score!

  • Venom Potency (0-30): How strong and fast-acting the venom is
  • Aggression (0-30): How likely the spider will attack
  • Delivery Efficiency (0-20): How capable the spider is of delivering venom when threatened
  • Human Encounter Risk (0-20): Likelihood of humans actually coming into contact with the spider

Each spider on this list is tiny to medium-sized but packs a potent punch!

Deadliest Spiders Ranked

Eastern Funnel-Web Spider
0
Venom: 30/30
30
0
Aggression: 30/30
30
0
Delivery Efficiency: 20/20
20
0
Encounter Risk: 18/20
20
0
Deadliness Score: 98/100
100
The Berserker: Absolute highest aggression and a 15 minute kill time make it the most lethal spider on the planet
Fangs are strong enough to pierce through soft leather shoes and even fingernails
Males leave their burrows in summer and autumn to find mates often entering homes
Capable of surviving underwater for hours by trapping air bubbles in its body hair
Its venom specifically affects the human nervous system while other animals remain resistant
Brazilian Wandering Spider
0
Venom: 30/30
30
0
Aggression: 29/30
30
0
Delivery Efficiency: 20/20
20
0
Encounter Risk: 18/20
20
0
Deadliness Score: 97/100
100
The Cytotoxin King: Possesses the most toxic venom by volume but often gives a warning display before striking
Does not spin a web but wanders the forest floor at night to hunt prey with keen eyesight
Often hides in dark places like banana plants or boots where it might bite if disturbed
Known to stand on its hind legs in a menacing threat display to warn potential predators
Its venom contains a potent neurotoxin that causes immediate pain and breathing difficulty
Sydney Funnel-Web Spider
0
Venom: 28/30
30
0
Aggression: 27/30
30
0
Delivery Efficiency: 19/20
20
0
Encounter Risk: 12/20
20
0
Deadliness Score: 86/100
100
Highly dangerous neurotoxic venom but lower encounter risk as it stays in moist sheltered burrows
Fangs point straight down like a tarantula rather than crossing in a pincer style
Becomes particularly active after heavy rainfall when burrows may become flooded
Maintains a tight grip on its victim and often bites repeatedly when attacking
The carapace covering the head is almost hairless and appears smooth and glossy
Black Widow Spider
0
Venom: 27/30
30
0
Aggression: 15/30
30
0
Delivery Efficiency: 18/20
20
0
Encounter Risk: 19/20
20
0
Deadliness Score: 79/100
100
High venom potency but generally shy unless its tangled web in a woodpile is disturbed
Recognizable by the bright red hourglass marking on the underside of its abdomen
Venom is roughly 15 times stronger than that of a rattlesnake by weight
Females are known for being doting parents that protect their egg sacs in silk cocoons
Feeds primarily on insects that become entangled in its strong sticky web
Redback Spider
0
Venom: 26/30
30
0
Aggression: 16/30
30
0
Delivery Efficiency: 18/20
20
0
Encounter Risk: 18/20
20
0
Deadliness Score: 78/100
100
Potent neurotoxin and high urban risk due to its habit of nesting in outdoor furniture
Female is easily recognized by her spherical black body with a prominent red stripe
Often squirts its victim with sticky silk from its spinnerets to immobilize them
Only the bite of the female is considered a serious medical threat to humans
Hatchlings are grey with dark spots and become darker with every molt
Brown Widow Spider
0
Venom: 24/30
30
0
Aggression: 14/30
30
0
Delivery Efficiency: 17/20
20
0
Encounter Risk: 17/20
20
0
Deadliness Score: 72/100
100
Potent venom but timid nature means it often plays dead rather than defending its web
Produces unique spiky egg sacs that make its nests easy to identify in gardens
Often found in sheltered spots like mailboxes or under the rims of plant pots
Venom is technically twice as toxic as a black widow but delivered in smaller amounts
Known for its mottled tan and brown coloring with an orange hourglass marking
Recluse Spider
0
Venom: 23/30
30
0
Aggression: 12/30
30
0
Delivery Efficiency: 16/20
20
0
Encounter Risk: 15/20
20
0
Deadliness Score: 66/100
100
Non-aggressive hunter with necrotic venom that causes tissue death if trapped against skin
Features a distinct violin-shaped marking on its back near the head area
Does not build a web to catch prey but wanders out at night to hunt insects
Long-lived and resilient species that can survive for months without food or water
Human contact usually occurs when clothing or bedding containing the spider is moved
Mouse Spider
0
Venom: 25/30
30
0
Aggression: 18/30
30
0
Delivery Efficiency: 14/20
20
0
Encounter Risk: 8/20
20
0
Deadliness Score: 65/100
100
Large powerful fangs and toxic venom but very rare encounters with humans
Often lives in trapdoor-covered burrows that can extend nearly 30 centimeters deep
Males are unusual because they wander in search of mates during the day
Many bites are dry bites meaning the spider does not inject any venom
Often mistaken for funnel-webs due to their stocky build and glossy black heads
Cupboard Spider
0
Venom: 20/30
30
0
Aggression: 12/30
30
0
Delivery Efficiency: 15/20
20
0
Encounter Risk: 16/20
20
0
Deadliness Score: 63/100
100
Frequently found in dark corners of homes where it builds messy tangled webs
Sometimes called the false widow because it looks similar to its more toxic cousins
A common sign of its presence is small white spots on the floor which are droppings
Its bite is usually no worse than a wasp sting and causes localized swelling
Known to occasionally prey on other spiders including dangerous black widows
Six-Eyed Sand Spider
0
Venom: 30/30
30
0
Aggression: 8/30
30
0
Delivery Efficiency: 15/20
20
0
Encounter Risk: 7/20
20
0
Deadliness Score: 60/100
100
Most potent necrotic venom but so shy and remote that it presents zero statistical risk
Buries itself just under the surface of the sand to ambush passing insects
Covered in small hairs called setae that hold sand particles for perfect camouflage
Can survive for up to a year on a single meal in harsh desert environments
It is often called a crab spider due to its flattened body and sideways stance

Overview & Honorary Mentions

It was tight at the top!  While the Wandering Spider has the most toxic venom by volume (‘purest’ poison), the Eastern Funnel-Web is biologically the more dangerous predator, having a significantly faster ‘kill time’ (as little as 15 minutes), and is more aggressive, whereas the Wandering Spider often gives a warning display or delivers ‘dry’ bites to conserve venom.

Eastern Australian Funnel-Web Spider
Brazilian Wandering Spider
Six-Eyed Sand Spider

The Cytotoxin King [Venom Potency]: Eastern Funnel-Web / Brazilian Wandering / Six-Eyed Sand Spider

Possesses the world’s most chemically devastating venom; capable of shutting down the nervous system or destroying tissue.

Eastern Australian Funnel-Web Spider

The Berserker [Aggression]: Eastern Funnel-Web

Relentless and fearless; this predator will stand its ground and strike repeatedly with a 15 minute kill time.

Eastern Australian Funnel-Web Spider
Brazilian Wandering Spider

The Piercing Specialist [Delivery Efficiency]: Eastern Funnel-Web / Brazilian Wandering Spider

Equipped with heavy-duty biological hardware; fangs designed to penetrate through leather and fingernails with ease.

Black Widow

The Uninvited Guest [Encounter Risk]: Black Widow

A master of urban adaptation; these species thrive in the shadows of human homes, leading to the highest number of annual bites.

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