Animal invaders can arrive by land, sea, or air. While most invasive species are unwelcome for one reason or another, some invaders up the creep factor simply by being giant versions of familiar animals. Just this week a horde of really, really big snails made the news by slowly taking over Florida. Here are some other awesomely oversize species that have infiltrated regions around the globe (but mostly in Florida). Above: Snails on Steroids Organism: Giant East African Land Snail, Achatina fulica Where: Florida When: 1966-1976, 2011-now Snails the size of rats are slowly invading Florida. The sluggish, oversized army of giant African land snails is poised to scar parts of Miami-Dade county with a comprehensive slimed-Earth strategy, a campaign that involves eating practically everything in sight -- whether plant, tire, or stucco -- and coating the county in disease-causing goo. It's not the first time these snails of unusual size have waged a glacial assault on this invasion-prone state. In 1966, a kid smuggled three of the snails into Miami from Hawaii; his grandmother later released them in her garden. Ten years, 18,000 snails, and $1 million later, the snails were gone. We'd hate to be that guy. Now, the snails are back -- and no one's sure who let them in. Since 2011, more than 115,000 snails have been plucked from sidewalks, gardens, and walls, at the rate of about 1,000 per week. With their bottomless appetites, ability to transmit meningitis-causing lungworm, and shells reportedly strong enough to blow out tires, the slow-moving behemoths are a risk to both public health and native species. Photo: Roberta Zimmerman, USDA APHIS, Bugwood.org

Mega-Mosquitoes Organism: Gallinipper, Psorophora ciliata Where: Florida When: Anticipated, summer 2013 Many times larger than your average annoying mosquito, gallinippers are not only overgrown but aggressive. They bite through clothing, they go after pets and fish, and they hunt for food 24 hours a day, delivering blood-sucking bites that hurt more than irritate. Their larvae eat tadpoles. Last year's bumper crop of the flying invaders has led University of Florida entomologists to suggest that a similarly large squadron will descend on the state this summer, if the rainy season is as soggy as expected. Photo: Marisol Amador, UF/IFAS

Preposterous Pythons Organism: Burmese Pythons, Python molurus bivittatus Where: Florida When: A while. Now. Too long. Regularly stretching more than a dozen feet from end to end, Burmese pythons are large, but not invincible. The snakes, which have slithered into Florida's Everglades National Park, have been known to explode after eating alligators. Controlling the population of these invasive snakes has been a challenge for the state; now, estimates suggest there are between 5,000 and 100,000 of the creatures prowling around, eating endangered critters and causing an ecological ruckus. As with the giant African land snails, it appears that people releasing pet snakes into the park have contributed to their numbers. People, knock it off. Photo: Mike Rochford, University of Florida/USGS

Rodents of Unusual Size __Organism:__Gambian Pouched Rat, Cricetomys gambianus Where: Florida When:~2000-2008, now In some countries, giant pouched rats are used to help detect land mines. In the Florida Keys, the 9-pound, 3-foot-long rats are an invasive species. The first wave of rogue rodents arrived around the year 2000, when an exotic pet breeder released several of the rats into the Florida wild. By 2008, the state thought they'd taken care of the potentially crop-destroying furries. In 2012, though, it appeared the Gambian giant rats were back, and officials have gotten to work setting traps baited with peanut butter and cantaloupe. Photo: U.S. Fish & Wildlife Service/Wikimedia

Super Shrimp Organism: Asian Tiger Shrimp, Penaeus monodon Where: Gulf of Mexico, Southeastern U.S. When: 2011-now Large and cannibalistic, Asian tiger shrimp make one hell of a nasty shrimp cocktail. The crustaceans can grow to more than a foot long, and are slowly skittering into the Gulf of Mexico and the waters off the U.S. Southeast. They're nocturnal hunters, hiding during the day and emerging in the dark to eat smaller shrimp species. Yum. Normally, these tiger prawns live in the Indian and Pacific Oceans; scientists aren't sure how the quarter-pound shrimp arrived in these non-native waters, but it isn't the first time they've been here. In 1998, scientists traced a similar shrimp outbreak to an aquaculture facility in South Carolina. Photo: Bill & Mark Bell/Flickr

Goliath Goldfish Organism: Goldfish, Carassius auratus Where: Lake Tahoe When: Now In the winter, Lake Tahoe is overrun by skiers; in the summer, by hikers. But it's also a giant goldfish bowl. For giant goldfish. In February, researchers from the University of Nevada, Reno, announced the discovery of oversized goldfish -- the presumed result of aquarium owners dumping fish in the lake. Now, scientists are concerned the giant goldfish (and their nonnative kin) are disrupting Tahoe's fragile ecosystem by messing with native populations of fish and algae. Photo: University of Nevada, Reno’s Aquatic Ecosystems Analysis Laboratory

Titanic Toads Organism: Cane Toads, Bufo marinus Where: Australia When: 1935-now Warty and wicked, cane toads can shoot poison from glands in their heads. The toads, which weigh as much as four pounds, were introduced to Australia in 1935 -- an ill-advised attempt to control the spread of crop-destroying cane beetles. Now, the original 102 toads have multiplied to more than 200 million. They're controlling the spread of most things -- including disease -- except the cane beetles. Photo: Blundershot/Flickr

Giant Grasshoppers Organism: Eastern lubber, Romalea guttata Where: Florida, Big Bend National Park When: 2002 (Florida), annually (TX) Among the better ways of killing a grasshopper is is pulling their heads off. That is, if you're dealing with the giant Eastern lubber, an oversized, colorful insect that's impervious to insecticides but that can ooze toxic foam if disrupted. In 2002, a swarm of these grasshoppers took over Central Florida neighborhoods, destroying vegetation and leaving way too many kids swinging two-by-fours. Photo: Houston Museum of Natural Science/Flickr

Scary Spiders Organism: Parawixia bistriata Where: Brazil When: February 2013 In February, a colony of spiders crawled in the skies over the Brazilian town of Santo Antonio da Platina. The spiders, called Parawixia bistriata, are large and sturdy, a type of colonial arachnid known for weaving individual webs that are linked up to create one massive interweb. Video: Acoisacoisada1/YouTube