I’m sitting with my son, and we’re watching an episode of Wild Kratts discussing hummingbirds. He’s enthralled, and I’m a little bored – I find the Wild Kratts message to be a little dubious at times, for reasons I won’t go into right now. My son turns to me, and asks “Did you know that there are real bloodworms?”

Well. I didn’t see this coming. Not from a show about hummingbirds, anyway. My response isn’t particularly inspired: “I did not know that.”

“They suck your blood! They live in the Amazon rain forest!”

Your guess is as good as mine. I figure it’s a testament to the way a five-year-old mind operates, because then we’re off to talking about how hummingbirds drink nectar (which is a fascinating bit of science in its own right, and one I should totally get into one of these days.)

This is a bloodworm:


And for a sense of scale, this is a bunch of bloodworms on someone’s hand:

Bloodworm hand

So, what are these gruesome looking things? Well, according to Sandworm and Bloodworm, a US Fish & Wildlife Service Biological Report, the common bloodworm is Glycera dibranchiata, also known as a beakworm or beak-thrower – two alternate common names that sound terribly interesting. They’re part of the Annelida phylum, which includes all ringed or segemented worms, and then the Polychaeta class, which consists of generally marine “bristle worms”. They’re found in the Gulf of Mexico, along the Atlantic coast from the Gulf of St. Lawrence to Floriday, and in the eastern Pacific from central California to Mazatlan. They are primarily predators.

bloodworm jaw

See that mouth? Those teeth are 13% copper. They also have pores that secrete a neurotoxin that is “especially effective on crustaceans”. They hunt through ambush, by digging burrows and then detecting vibrations as the prey moves above them.

So, does the bloodworm suck blood? Well, not according to the report I’m working from. They’re called bloodworms because they are bright red, thanks to their hemoglobin. They will bite, though, and the bite can cause a reaction similar to produced by bee and wasp stings – the venom closely matches that of those insects.

Now, why is it also called a ‘beak-thrower’? It turns out that it has “a pharynx that can be rapidly everted, allowing the worm to grab food and pull it into the mouth”.


Kind of like that, I guess.

Do bloodworms live in the Amazon? I… don’t know.  Internet searches for variations on “Amazon bloodworm” pretty much turn up opportunities to buy freeze-dried bloodworms from  According to Wikipedia, however, bloodworm is the common name for all of genus Glycera. The common bloodworm is a North American animal, but there are something like 81 species found in genus Glycera and the article doesn’t really discuss geographical ranges.

But wait! It gets more convoluted. There is something called a blood fluke, which a few sites I visited called “bloodworms”, that does live in South America!  This is a blood fluke:

blood fluke

Blood flukes, part of genus Schistosoma, aren’t particularly closely related to bloodworms. They’re part of the same kingdom (Animalia) but they’re in the Platyhelminthes phylum, making them part of a phylum of bilateral unsegmented foft-boied invertebrates. They’re also tiny, tiny critters. The picture above was taken by an electron microscope. Five species of blood flukes – Schistosoma mansoni, S. haematobium, S. japonicum, S. intercalatum, and S. mekongi drink human blood. Hang on, because this gets unpleasant.

Blood fluke larvae start by parasatizing freshwater snails. Their eggs hatch into miracidia (a larval form) then transform into sporocysts (another larval form) if they successfully locate a snail and reproduce asexually, producing hundreds of cercariae (yet another larval form) which drift about in the water. The cercariae can survive for about 48 hours, during which time they will use enzymes to penetrate human skin if they come into contact. This causes them to transform into shistosomulae (again, another larval form), which get into the human blood stream and mature in 6-8 weeks – they’re about 1-2 cm long at this point. They then mate and lay eggs on capillary walls at the rate of 300 – 3,000 eggs per day. The eggs, when mature, produce enzymes that let them penetrate rectal veins and intestinal walls, allowing them to escape the body.

So, yeah. The medical name for parasitism by these critters is schistosomiasis (sometimes known as bilharzia or snail fever), and more than 200 million people may suffer from it. Symptoms of schistosomiasis may include chills, cough, diarrhea, fatigue, fever, and muscle aches. Also anemia, learning difficulties, and malnutrition in children. And if the parasitism continues for years, it can result in inflamation of the liver, bladder, and lungs, and possible paralysis and seizures.

Isn’t nature wonderful?

To sum up, bloodworms don’t appear to live in the Amazon or suck blood. They’ll just bite you and it’ll hurt like a bee sting. Blood flukes, on the other hand, do live in the Amazon. And in pretty much all the fresh water in Africa, the Caribbean, southern China, southeast Asia, and the Middle East. And they will quite cheerfully suck your blood. And swim in it. And have wild parasitical worm orgies in it.