Heavy-bodied pit viper up to 2.5 m. Responsible for more snakebite deaths in Central America than any other species — "the ultimate pit viper".

Highly potent hemotoxin causes catastrophic tissue damage and bleeding. Without antivenom, mortality reaches 7–9%. Aggressive when cornered.

Lowland forests, plantations, banana fields from southern Mexico through Guatemala, Honduras, Nicaragua, Costa Rica, and Panama.

Active hunter at night; sometimes climbs into low vegetation. Females give birth to up to 80 venomous neonates.

Yellow-brown scorpion up to 9 cm. Endemic to Durango and Sinaloa states in Mexico. Historically responsible for thousands of deaths — 1,500+ per year before antivenom.

Powerful sodium-channel neurotoxin causes salivation, vomiting, pulmonary edema, and cardiac failure. Children most at risk; deaths still occur despite Faboterápico antivenom.

Durango, Sinaloa, Nayarit, and adjacent Mexican states. Hides in homes, woodpiles, and under rocks.

Climbs walls and ceilings. Active at night. Stings people in beds and shoes — drops from ceilings into cribs. Glows under UV light.

Yellow-tan scorpion 6–7 cm with thin tail. One of the most medically important species in central and southern Mexico — Morelos, Guerrero, Michoacán.

Highly potent neurotoxin. Combined with C. tecomanus, responsible for the highest scorpion mortality in Mexico's Pacific states. Antivenom widely deployed.

Tropical and subtropical zones of Morelos, Guerrero, Michoacán, Mexico State, Puebla. Common in rural homes.

Nocturnal. Hides under bark, stones, in cracks of adobe walls. Aggressive when cornered — can sting through thin clothing.

Small dark scorpion (up to 4 cm) endemic to Nayarit, Mexico. Despite tiny size, has the most potent venom of any Mexican scorpion — discovered as the source of the first scorpion neurotoxin ever isolated (Noxiustoxin, 1982).

Lethal dose only 5 micrograms in a 20g mouse — among the most potent neurotoxins known. Targets potassium channels; rapid respiratory and cardiac failure without treatment.

Endemic to Nayarit state, Mexico. Found in tropical lowlands, hiding under bark and rocks.

Nocturnal. Quick to sting when disturbed. Used extensively in research because of its remarkable toxin biochemistry.

Heavy-bodied pit viper up to 2 m with diamond pattern and black-and-white banded tail. The most widespread rattler in the southwestern US and northern Mexico.

Hemotoxic venom destroys tissue. Causes more snakebite deaths than any other species in the US — about 5–6 per year.

Deserts, scrubland, and rocky outcrops from California to Arkansas, plus most of Mexico.

Ambush predator. Rattles as warning before striking, but startled snakes can bite without warning. Active April–October.

Up to 1.8 m. Unlike most rattlesnakes, has potent neurotoxic venom (similar to mamba). Common in dry interior valleys of Central America.

Neurotoxin causes paralysis and respiratory failure — different symptoms than US rattlers. Antivenom essential within hours.

Dry tropical forests, savannas, and farmland of Mexico (Yucatán), Guatemala, Belize, Honduras, El Salvador, Nicaragua, Costa Rica.

Nocturnal in hot weather. Often found near villages and in agricultural areas. Causes most snakebite deaths in Costa Rican Pacific lowlands.

Brightly banded red-yellow-black snake up to 1.2 m. Related to cobras and mambas — the only elapid in eastern North America. "Red touch yellow, kill a fellow."

Powerful neurotoxin can cause respiratory paralysis. Bites rare — only ~25 per year in US — but require antivenom (which is increasingly scarce).

Pine flatwoods, scrub oak, leaf litter of Florida, Georgia, Alabama, Mississippi, Louisiana, parts of Texas and northern Mexico.

Secretive and reluctant to bite — must chew to inject venom. Often confused with non-venomous milk snake.

Third-largest cat — up to 100 kg. Spotted rosettes with central dots distinguish it from leopards. In North America found in Mexico and rarely Arizona/New Mexico.

Strongest bite force of any cat — pierces turtle shells and skulls. Attacks on humans rare but occur in Mexican rainforests.

Tropical rainforests of southern Mexico (Chiapas, Yucatán), Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama; rare strays into Arizona.

Solitary, mostly nocturnal. Excellent swimmer — hunts caimans, capybaras, deer. Stalks before pouncing.

Largest small cat in the world — up to 100 kg, body 2.5 m including tail. Can leap 5 m vertically and 12 m horizontally. Most widespread big cat in the Americas.

Attacks on humans are rare but documented — about 1 fatal attack every 2 years in North America. Targets joggers, cyclists, and children. Strikes from behind.

Mountains, forests, deserts from Canadian Rockies to Patagonia. Wide range of habitats.

Solitary, crepuscular, silent. Doesn't roar — emits eerie screams during mating. Stalks prey for hours.

Up to 5 m. Greenish-grey with narrow, V-shaped snout. Found in saltwater and brackish coastal areas — unique among crocs in tolerating both fresh and saltwater.

More dangerous than American alligator. Several fatal attacks per year in Mexico, Central America, and Caribbean. Ambushes from water.

Coastal mangroves, estuaries, lagoons of southern Florida, Mexico, Belize, Guatemala, Honduras, Costa Rica, Panama, Cuba, Hispaniola, and northern South America.

Less docile than alligator. Excellent saltwater swimmer — has crossed 100+ km of open ocean. Active at night.

Glossy black female with red hourglass on abdomen. About 13 mm body. Males harmless. The 'classic' black widow of American folklore.

Alpha-latrotoxin causes severe muscle cramps, hypertension, sweating ('latrodectism'). Fatalities now rare with antivenom; ~2,500 bites per year in US.

Woodpiles, sheds, garages, outdoor toilets across southern and eastern US, Mexico.

Builds messy tangle web in corners. Bites only when pressed. Females cannibalize males rarely (myth exaggerated).

Up to 5 m with vertical tiger-like stripes (fade with age). Eats almost anything — license plates, tires, and human remains have been found in their stomachs.

Second only to great white in unprovoked human attacks. Common in Caribbean and Hawaiian waters. Slow but powerful — strikes once and waits.

Tropical and subtropical waters — Florida, Caribbean, Gulf of Mexico, Hawaii.

Solitary, mostly nocturnal. Migrates long distances. Females birth up to 80 live pups.

Dark brown bug 2 cm long with red-orange edges. Bites face at night (hence 'kissing') while you sleep. Transmits Chagas disease — a chronic illness affecting heart and digestive system.

About 300,000 people in US infected with Chagas (mostly immigrants). 30% develop fatal heart damage decades later. Vector range expanding north with climate change.

Wood-rat dens, log piles, dog kennels of southern US (Texas to Georgia), all of Mexico, Central America.

Active at night. Defecates near bite site — parasites enter through bite wound or rubbed-in feces.

One of only two venomous lizard species in the world. Up to 90 cm. Beaded black-and-yellow scales. Endemic to western Mexico and Guatemala.

Venom causes severe pain, swelling, and drops in blood pressure. Rarely fatal in adults but extremely painful — won't let go when biting.

Dry tropical forests and thorn scrub of western Mexico (Sonora to Oaxaca) and southern Guatemala.

Slow, mostly underground. Active in spring after rains. Bite triggered by handling — chews to deliver venom through grooved teeth.

'Killer bee' — hybrid of African and European honey bees, escaped Brazilian lab in 1957. Spread north and arrived in southern US in 1990; now in Texas, Arizona, Nevada, California, Florida.

Individual sting like normal bee, but they swarm aggressively — attacking in 100s for minor disturbance, pursuing victims 400 m. About 1–2 deaths per year in US.

Southern US (Texas, Arizona, California, Florida), all of Mexico, Guatemala, Honduras, Nicaragua, El Salvador, Costa Rica, Panama, Belize.

Easily provoked by vibration, sound, dark colors, exhalation. Stays angry for 24+ hours after disturbance.

Pale yellow-tan, 7–8 cm. The most venomous scorpion in North America. Glows brilliantly under UV light.

Neurotoxic sting causes severe pain, numbness, and in children — convulsions and respiratory failure. Antivenom dramatically reduces mortality.

Rocky deserts and palm oases of Arizona, southern Utah, southeastern California, parts of New Mexico and northern Mexico (Sonora).

Climbs walls, hides under bark and stones. Active at night. Sometimes enters homes. Can survive being frozen overnight.

Reddish-brown ant 2–6 mm. Invasive from South America since 1930s; now infests southern US from Texas to Virginia. Aggressive when nest disturbed.

Stings cause burning pustules. Allergic reactions can cause anaphylactic shock — about 80 deaths per year in US attributed to fire ants.

Open sunny areas — lawns, fields, roadsides — across southern US, Caribbean, parts of Mexico.

Builds large mound nests up to 60 cm tall. Step on a mound, hundreds swarm out and sting in unison.

Largest scorpion in North America — up to 15 cm. Yellow body covered with brown hairs. Massive but its size is its defense — venom is mild.

Sting comparable to a bee or wasp. Only dangerous to those with allergies. Not a medical threat — but its sheer size is alarming.

Sonoran and Mojave deserts of Arizona, California, Nevada, Utah, and northwestern Mexico (Sonora, Baja California).

Nocturnal burrower — digs burrows up to 2.5 m deep. Hunts other scorpions, lizards, and insects. Glows brilliantly under UV light.