What Are Sand Fleas?

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Sand fleas are a confusing lot because they have been given different names and identities. In this lesson we're going to clear all that up by explaining what sand fleas are, what they aren't, and what you can expect from them if you happen to meet them.

A Pesky Party Pooper

There's nothing quite like a day at the beach. The sun, the surf, music, good friends, and sand fleas. What, what? No one invited them along! Unfortunately, the beach is just one place that sand fleas call home. These tiny crustaceans are often referred to as insects, and the name 'flea' certainly doesn't help. But they are in fact not insects at all, and instead are related to other crustaceans such as lobsters, crabs, shrimp, and crayfish.

Sand fleas look like tiny shrimp in the sand
sand flea

A Flea by Any Other Name

Much of the confusion about what a sand flea comes from the multitude of names people call them. Sandhoppers, beach fleas, beach hoppers, hop-alongs, and biting midges are just a few. And they get these names because like fleas and midges they do bite and leave a red, itchy welt behind. There is also confusion between mole crabs and sand fleas. Yes, they are both crustaceans, but mole crabs are in the order Decapoda while sand fleas are in the order Amphipoda.

Sand Flea Facts

Amphipods like sand fleas are small, shrimp-like critters that live in marine and freshwater environments, with some being terrestrial. Sand fleas obviously prefer sandy locations like beaches and coastal areas. But they also live in marshes and desert areas. Unlike real fleas, which will gladly hitch a ride with you, sand fleas prefer to stay at the beach. But watch out because female sand fleas may literally get under your skin to lay her eggs!

Those eggs will be laid into a pouch that is on the underside of the female. Within a few weeks, those eggs will hatch and the babies will come out looking a lot like their adult counterparts. Most of these guys will live to only about a year, and in general, will produce only one set of eggs.

Mole crabs are often confused with sand fleas, but each belongs to its own order. Mole crabs are also larger and do not really look like shrimp
mole crab

Sand fleas are small, but some of them may be as big as an inch or so long. Much like a female mosquito bites you because she needs your blood to produce her eggs, sand flea females also need your blood for the same reason. The after-effects of the bite are also like that of a mosquito - the bite itself isn't the problem, it's your body's reaction to her saliva that makes it itch and swell. And despite the female's vampire-like desire for your blood, sand fleas actually feed on organic matter. Seaweed is a big hit, as is other detritus.

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