They're not monsters, but they are a problem for native flora and fauna. Here are ten of the ecological troublemakers finding their way into American landscapes and waterways.

Six lionfish, which are native to the Indian Ocean, were accidentally released into the Caribbean in 1992 when an aquarium in southern Florida was destroyed by Hurricane Andrew. Lionfish have since been detected in at least 30 locations in the U.S. and many more locations throughout the Caribbean; they and are believed to threaten native marine wildlife in Venezuela and the livelihoods of coastal towns dependent on fishing and tourism. Photo: Reuters/Carlos Garcia Rawlins

The Gypsy Moth is the classic invader, hitching a ride to America in 1868 or 1869. Unlike many of the species below, we've learned a lot about controlling it, and it not occupies only a third of its former range.

South Florida is fighting a growing infestation of one of the world's most destructive invasive species: the giant African land snail, which can grow as big as a rat and gnaw through stucco and plaster. This one is coming for you, now: walk for your lives! Photo: Florida Department of Agriculture Division of Plant Industry.

The Tiger Mosquito, native to Asia, is now found in abundance in the U.S. Photo: John Tann

Pictured in here in Casco Bay in Freeport, Maine, the European green crab is another invader. Encouraged by rising ocean temperatures, they are munching their way north through Maine's clam flats, threatening the state's third-largest fishery and an iconic summer treat for tourists. REUTERS/Dave Sherwood

Researchers are unsure if the Soybean cyst nematode is truly an invasive species, but its modern spread is alarming. The nematode causes stunted growth and reduced crop yields. Photo: USDA

In this infamous photo, a Burmese Python has exploded after foolishly trying to eat an alligator whole. Pythons, originally acquired as pets and dumped by their owners, have thrived in Florida's swamps since the 1990s.

Invasive species include many plants, choking out native flora and spreading uncontrollably, such as the kudzu photographed here in infrared by Kyle May (cc)

Cane toads, native to central and south America, can grow to the size of a small dog. They've been found in Hawaii and, of course, Florida, where they were introduced in 1936. There is a silver lining to this invasion: when caught, reports the BBC, they may be gassed and liquidized to make "excellent fertilizer." Photo: Akex Popvkin (cc)

Wild boar are not native to the U.S., but came with European settlers so long ago they are rarely counted among invasive species. Nonetheless, the huge eurasian hogs have become a "pandemic", beyond the control of hunters and trappers, damaging native plants and crops and forcing out native species: "We're not going to barbeque our way out of this problem."

Photo (top): Gypsy Moth. Photo: followtheseinstructions