Blood Sucking Critters

By: Dr Andrew Impey

What do ticks, leeches, mites, fleas, beetles, flies, lampreys, catfish, bats and moths have in common?

Well, they are unlikely to feature in most people's list of favourite animals, and they are also unlikely to be the subject of the next Disney film.

However, the answer I was actually after is that they are all groups of animal which practise haematophagy. Put simply, they want to suck your blood.

No prizes for guessing that answer - I think I may have given it away with the title. However, a few on the list might have come as a surprise. Mites, ticks and leeches are rather self explanatory and you don't have to be a taxonomist to be able to name some blood sucking flies or bats, but beetles? Catfish? MOTHS? All will be explained.

Bloody Bugsuckers

First off, bugs. Actually to be more specific, assassin bugs. Certain species of South American assassin bug require blood meals to complete their life cycles.

In the case of the delightfully named bloodsucking conenose that blood is human.

Conenoses, also known as Mexican bed bugs, inhabit houses in Northern South America and parts of the Southern United States. Although assassin bugs are generally solitary insects, the conenose is a gregarious species. It hangs around in gangs of 10 or more waiting to pounce on the next unsuspecting victim.

You might think it safer to head for the nearest river, rather than hang around waiting to be attacked by a pack of bloodsucking conenoses. You'd be wrong. You might then be risking the attentions of a little South American catfish, known as the candiru.

Feisty fish

You may well have heard tall tales of fish in the Amazon that can swim up a stream of urine and become lodged in - well, it becomes lodged where a stream of urine comes out.

Candiru are the source of these legends. They're small (about five inches in length) parasitic catfish which normally feed from the gills of larger fish. They enter the prey fish's gill opening, stick out their backwards pointing spines and help themselves to a bellyful of fish blood.

Unfortunately, being the small dim-witted catfish they are, they occasionally seem unable to tell the difference between a fish and a person bathing. They also seem unable to notice that the openings they find on people aren't gills. I probably don't need to explain what happens next. There is certainly no need to mention the word urethra.

This kind of occurrence does appear to be a genuine mistake, as candiru attacks on people are always fatal for the fish, and often for the victim without surgery.

Moths that go bump in the dark

Still, once you have managed to uncross your legs, have a think about the next sentence: 'Etsia rikki! Se on kyynelyokkonen!' For our non-Finnish readers, that loosely translates as 'Look out! It's a vampire moth!', something that is increasingly said in Southern Finland.

Thanks to global warming, this rare species of blood-hungry critter is on the increase in Finland.

The Finnish nature magazine Suomen Luonto describes how the moth is able to puncture human skin and deliver a painful bite. This news finally gives those of us with an irrational fear of moths (lepidopterophobia) some small justification for being terrified by butterflies with unusual sleep patterns.

But despite the lepidopterophobics, I feel animals that feed on blood are unjustly grouped with extortionists, blackmailers and evil lawyers as 'blood suckers'. It is an injustice that must be put straight.

Many of nature's haematophages (haem = blood, phage = eater - not rocket science this linguistics malarkey is it?) don't actually do any sucking at all, preferring to let blood pressure to do all the hard work.

Why not to be lazy

Refusal to do a bit of hard work can backfire on some blood eaters, such as the humble mosquito.

A mosquito's mouth-parts sometimes become stuck in its victim. Then, thanks to a heady mix of anti-coagulants in the mosquito saliva, and the victim's own blood pressure it fills up, and up, and up, until... pop! Goodbye Mr Mosquito.

Now this brings me finally to an interesting common link between all of these animals, which is more significant than that they look ugly and will try and bite you.

Perhaps, just as we are genetically conditioned to be scared of poisonous snakes and spiders, we too are conditioned to be repulsed by parasitic blood eaters.

Most common haematophagic animals spread disease. Vampire bats can give you rabies, assassin bugs Chagas disease (a condition that can lead to heart problems), fleas can spread bubonic plague and mosquitoes malaria.

None of these animals actually cause these diseases, but because of their blood-based diets they act as vectors. It would be genetically advantageous for an individual to be repulsed by and so avoid these animals, even if the amount of blood taken in a meal is negligible.

So next time you see someone running in terror from a harmless moth, think about it; maybe it's because they're genetically programmed to look after their own blood. Or maybe it's just because they're a big wuss.

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Andy worked for four years studying ducks (no stop laughing, he really did). He went into his PhD thinking he was going to save the world (albeit from ducks) and now spends him time lovingly preening strange but true and other aspects of null-hypothesis

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