1. Pythons
2. Alligators
3. Toads
4. Crocodiles

No one knows how Burmese pythons were originally introduced into the Florida Everglades, but it only takes two of them to make babies. These pythons give birth to about four dozen babies every year. The growth of their population may be why the population​s of raccoons, opossums, bobcats, marsh and cottontail rabbits, as well as foxes, are down.

1. Woodpeckers
2. Emerald Ash Borer
3. Moth Larvae
4. Inch Worms

Although they call Russia, China and Japan home, the Emerald Ash Borer arrived in southeastern Michigan in 2002 and has spread from there, killing tens of millions of ash trees in its growing path. Adult beetles lay eggs on the bark of ash trees and their larvae feed on the nutrition transportation tissues that the tree needs to survive.

1. Mink
2. Snow Leopards
3. Nutria or Swamp Rats
4. Racoons

Imported from South America for their fur in the 1930s, their population skyrocketed once demand stopped for their fur. Worse yet, female nutria or swamp rats give birth to litters of up to 14 then are ready to mate within two days.

1. Blue Jays
2. Goldfinches
3. Cardinals
4. European Starling

Shakespeare enthusiasts in the 1890s introduced these birds to the U.S. Today, with a a population of about 200 million, they travel in flocks and use their numbers to bother large animals (cows, horses, etc.) until the animals move off so they can take their food.

1. Whitefish
2. Bass
3. Salmon
4. Alewives

Alewives are a small herring that eat Lake Trout eggs and compete with juveniles for zooplankton. If a trout or landlocked salmon eats alewives, they get a vitamin deficiency that can kill their larval.

1. Northern Snakehead
2. Northern Pike
3. Wide-Mouth Bass
4. Flathead Catfish

The Northern Snakehead hails from China and Korea but was found in the Chesapeake Bay watershed and is spreading to Delaware and Virginia. It looks like a cross between a python and an electric eel. With no predator and the female's ability to produce up to 100,000 eggs, it is a huge challenge to keep the population under control.

1. Mosquitoes
2. Stink bugs
3. Grasshoppers
4. Crickets

Brown Marmorated Stink Bugs were found in 1998 in Allentown, Pennsylvania. It was thought the stink bugs came from a cargo ship that probably stopped or came from China where these bugs call home. Stink bugs destroy fruits and vegetables and were recently detected in South Carolina, Georgia and Florida.

1. Wild Dogs
2. Wild Boars
3. Black Bears
4. Mountain Lions

Wild Boars are known to eat the eggs of any ground nesting bird as well as devour acorns and chestnuts. Already established in 47 states, there are huge numbers in Texas, Florida, Georgia and North Carolina. Because of their destructive nature, in most areas, hunters are allowed to shoot them on sight.

1. Sharks
2. Puffer Fish
3. Lionfish
4. Eels

Originally admired for their beauty, the Lionfish is a swimming pig, consuming most every living thing in a coral reef. Although originally found in the Pacific, they are now found most everywhere from the Gulf of Mexico, to the Atlantic and the Caribbean Sea.

1. Norway Rats
2. Norway Pigeons
3. Spotted Mice
4. Giant Cockroaches

Running from ground to tree branch, Norway Rats (also known as Brown Rats and Sewer Rats) will eat everything from eggs in nests to young chickens, garbage and even wood! Introduced in 1775, they now live everywhere in the country.

1. Rattlesnakes
2. Pythons
3. Lizards
4. Tegus

Tegus look like little brown anolis lizards. Unfortunately, when pet stores released the Tegus into the wild in the Florida Keys, they did similar damage in Florida as the Pythons. They are on the verge of reaching into southern Georgia with no known predators in sight.

1. Cabbage Maggot
2. Asian citrus psyllid
3. Cutworms
4. Colorado Potato Beetle

The bacteria that the Asian citrus psyllid carries has many names: "huanglongbing", “yellow dragon disease” and “citrus greening” but they all cause the same destruction. From deformed roots to fruits dropping prematurely, the tree slowly dies. Discovered outside Miami in 2005, it spread to 31 other counties within two years.

1. King Cobra
2. Banded Water Snake
3. Rattlesnake
4. Brown Tree Snake

Native to Australia and Indonesia, the brown tree snake was accidentally introduced in Guam in the 1950s. Today, there are no longer any birds left. And the brown tree snake in now finding lizards as a tasty substitute.

1. Bluegrass
2. Bermudagrass
3. Cheatgrass
4. Centipedegrass,

Cheatgrass is an invasive grass that has established itself through the western U.S. It competes with native grasses and fuels intense fires. It pushes out sage-grouse and other sage-dependent species.

1. Mayflys
2. Stoneflys
3. Zebra mussels
4. Piranhas

Although native to Eastern Europe and Western Russia, zebra mussels were found in the Great Lakes region in the 1980s, and had spread through all of the lakes by the 1990s. They compete with fish for plankton and clog pipes with their colonies.

1. Laternfly
2. Firefly
3. Mosquito
4. Gnat

The laternfly was discovered in Berks County in 2014, and has spread to neighboring counties. It is so destructive because it has an abundance of food it can eat, feeding on more than 70 species, including grapes, apples, stone fruits, and pines.

1. Gnats
2. African Bees
3. Honey Bees
4. Mosquitoes

Although the Zika virus was limited to the equatorial belt, it is now in the U.S, transmitted by mosquitoes. According to the Centers for Disease Control*, in 2017, 418 symptomatic Zika virus disease cases were reported in the U.S. So far, there have been no reports in 2018. *https://www.cdc.gov/zika/reporting/2017-case-counts.html

1. Mitten Crab
2. Hat Crab
3. Fiddler Crab
4. Snow Crab

Known for eating the eggs of spawning salmon, trout and sturgeon, the Mitten Crab is a serious threat to the freshwater, estuarine and%0Dmarine ecosystems One mitten crab was found in the Columbia River in 1997.

1. Red Swamp Crayfish
2. Signal Crayfish
3. Northern Clearwater Crayfish
4. Virile Crayfish

The Red Swamp Crayfish eat the plants, snails, fish, and amphibians, as well as take up residence in the native crayfish habitat. To identify them from native crayfish, you'll note the red swamp crayfish claws are covered with red, white or black bumps (tubercules).

1. Old World Climbing Fern
2. New World Ivy
3. Poison Ivy
4. Hemlock

Old World climbing ferns sprout on trees and don't allow native vegetation to bask in the sun all over east-central Florida. One of the reasons why it is so hard to eradicate is because the fern has the ability to “resprout” along each climbing leaf. That means if you leave a SINGLE leaf to thrive, a new fern will sprout.

1. Corn
2. Wheat
3. Poison Ivy
4. Tropical Soda Apple (TSA)

Foliage and stems from the Tropical Soda Apple (TSA) are hard for the cattle to digest which makes it a big problem since Tropical Soda Apple is known to grow in pastures. The current hypothesis is that cattle carrying undigested TSA seeds that were imported from Brazil may have accidentally introduced it in the U.S.

1. Water Hyacinths
2. Water Lily
3. Grass Pink Orchard
4. Milk Weed

You may be surprised to learn that an acre of water hyacinths can weigh up to 200 tons! That means it can easily jam rivers and lakes with tons of floating plant matter. This invasive species takes over the body of water completely, pushing out any native plants.

1. Kudzu
2. Wisteria
3. Poison Ivy
4. Black-Eyed Susan

Although the Kudzu was introduced at the Japanese pavilion in the 1876 Centennial Exposition in Philadelphia, the vine didn't take hold here until nearly 55 years later when it was reintroduced as a way to stop soil erosion on farms. Workers were paid $8 per acre to sow topsoil with the invasive vine that grows quickly and shades out the native species.

1. Tornado bees
2. Meany bees
3. Killer bees
4. Killer Hornets

Due to the violent attacks of this hybrid of African and European honeybees, the name "Killer Bees" became the popular way to reference this invasive species. This hybrid comes from Brazil and while its sting is no more poisonous than one of a honeybee, the large numbers of killer bees that attack together can prove fatal to animals and people.

1. Orange Roughy
2. Grouper
3. Asian Carp
4. Pike

Asian carp eat plankton which includes algae and other microscopic organisms that native fish and mussels need to survive. The fish were brought from Southeast Asia because they can help in many areas, including keeping retention ponds clean. They entered the Mississippi River as a result of flooding.

1. Spruce Sap Sucker
2. Hemlock Woolly Adelgid
3. Longhorn Bettle
4. Leaf Bettle

The Hemlock Woolly Adelgid (HWA) sucks sap from hemlock and spruce trees, weakening and eventually killing the tree. They also lay their egg sack on the underside of hemlock branches, which look woolly or like small tufts of cotton. They were accidentally introduced here from Japan nearly 70 years ago.​

1. Rosa Multiflora
2. Larkspur
3. Scabioius
4. False Goat's Beard

Rosa multiflora is considered an invasive species In eastern North America due to its faster growth and ability to push out native roses from their habitat. It was introduced from Asia to help in soil conservation along with creating natural hedges to contain grazing pastures.

1. Spiny Waterflea
2. Crustacean
3. Chigoe Flea
4. Picnic Flea

The Spiny Waterflea entered the Great Lakes in ballast water released from ocean-going ships. It is able to multiply so quickly because its unappetizing spiny tail keeps it from becoming dinner for the fish.

1. Mahi, Mahi
2. Tilapia
3. Rainbow Smelt
4. Catfish

From eating the larva of other fish, to competition for zooplankton, the Rainbow Smelt have expanded their impact throughout North American freshwater lakes for more than 100 years. The infestation resulted from rainbow smelt having been​ stocked into Crystal Lake, Michigan, in 1912.

1. Sardine
2. Atlantic Cod
3. Atlantic Bluefin Tuna
4. Ruffe

Appearing in the Great Lakes (Lake Superior to be exact) the Ruffe came in the ballast water of an ocean-going vessel. High growth rates along with high reproductive rates and the ability to adapt to a myriad of environments, has made this small fish a serious threat to other species.

1. Tapeworm
2. Ticks
3. Sea Lamprey
4. Flukes

Sea lampreys use their sharp teeth to cut through scales and skin and then use their sucking disk to digest a fish’s body fluids until it dies. Each sea lamprey can kill 40 or more pounds of fish.

1. Red Fire Ants
2. Milkweed Bug
3. Termites
4. Carpenter Ants

When disturbed, red fire ants emerge aggressively, crawl up vertical surfaces, then bite and sting non-stop. They have displaced other species of fire ants native to Texas and continue to populate in other areas.

1. Cownose Ray
2. Grasshoppers
3. Mayflies
4. Ants

Virginia officials hope the public will agree that the Cownose Ray, rebranded as "Chesapeake Rays," are a tasty substitute for veal. They hope the thinning of Cownose Rays will protect the Chesapeake Bay's oyster industry.

1. Tree Killer Ants
2. Mountain Pine Beetles
3. Black Flies
4. Deer Flies

When insects bore into pine trees, the trees fight back by increasing their flow of sap, a defense that forces the invaders out of the holes in the bark. Unfortunately, pine beetles produce a fungus that disables this defense. Eventually, unable to absorb water, the pine tree withers and dies.

1. Brown Tree Snake
2. Python
3. Rattlesnake
4. Asian Mongoose

Originally brought to Hawaii to help control an overwhelming rat population, the Asian Mongoose chose not to eat rats and instead eat something easier: eggs and baby birds, specifically enjoying Hawaii's state bird, the Nene or Hawaiian goose.