What to Know About South Florida's Migratory, Home-Invading Land Crabs | Miami New Times
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What to Know About South Florida's Migratory, Home-Invading Land Crabs

Everyone knows how to deal with invasive arthropods like spiders and cockroaches, but what about their much larger cousins?
Image: A blue land crab is pictured outside its underground burrow.
A pair of blue land crabs snuck into a Miami resident's home, causing a stir on social media. Photo by Mason Smith of FWC via Flickr
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Creepy, crawly arthropods have been invading homes and terrorizing people with their presence since the dawn of human history, so much so that knowing how to deal with interlopers like spiders and cockroaches is an evolutionary trait. But would instinct kick in if one of their much larger arthropod cousins — say, a blue land crab with a five-inch-long claw — crept its way into your home?

For one unfortunate Redditor, the answer seems to be no.

How did this crab get in my house? 2 days in a row!
byu/Interesting_Neat_760 inMiami

The poster shared an image of a blue land crab, which apparently was the second one to sneak into their home. The post has garnered nearly 2,000 upvotes and more than 200 comments, with several humorous takes on the situation, which beg questions like: How did it get there? Are they dangerous?

To understand exactly what kind of Looney Tunes situation this person was in, New Times sought out University of Miami Professor Maria Criales, curator of the Voss Invertebrate Collections and adjunct assistant professor of marine biology.

She identified the animal in the photo as a blue land crab (Cardisoma guanhumi), a common species in the family Geocarcinidae, which includes other land crabs.

"Despite its name, only the males have a bluish coloration," she tells New Times. "These crabs dig burrows on land, so it is not surprising that one was found inside the house. This species occurs in the western tropical Atlantic, from Brazil to Florida, and is common throughout the Caribbean, the Gulf of Mexico, the Bahamas, and Florida."

Unlike many of their seafaring relatives, these crabs spend most of their time on land and only return to the water to spawn, like reverse sea turtles.Yes, these crabs migrate up to six miles from their burrows to the ocean, unlike many of their land-dwelling cousins. Their closely related cousin, the black land crab, creates an "extraordinary sight" when the juveniles, who are red, return to Providencia Island in the Caribbean. Criales tells New Times that "the roads turn red."

"After approximately two weeks, the eggs hatch into zoea larvae, which remain in the plankton for about four weeks," she explains. "Following development, the megalopae [juveniles] migrate back to land. Several spawning events may occur per year, with the season varying across the species' range. In Florida, spawning lasts from June to December and peaks in October and November. During this period, large migrations of crabs can be observed."

So if you see one out and about this fall, mind your business; it may be late for a beachside booty call.

They aren't known for being dangerous, anyway, Criales said, "but they have large claws and if they feel threatened, they can bite you."

Marine biologist Elizabeth Mills offers tips on how to safely pick up "any type of crab found around the world " in a YouTube video.

Reach for the farthest two points on the crab's body from behind to avoid the claws. By hoisting them up from behind, with their claws facing away from you, "they should never be able to pinch you," Mills explains. From there, take the crab outside, preferably near a water source.


Depending on the time of year, you definitely shouldn't kill a blue land crab, which the Redditor admits they accidentally did to the first one that broke into the home. In Florida, it's illegal to kill the crabs during spawning season — July 1 through October 31, according to the Florida Fish and Wildlife Conservation Commission.

Outside of the prohibited season, people may kill and bag up to 20 blue land crabs a day. The meat is supposedly delicious, Criales tells New Times, "but I haven’t tried yet. It is a very common meal in some Caribbean Islands."