Are no-see-ums a thing?
July 3, 2013 11:50 AM   Subscribe

What is the smallest animal species that a single individual of can cause a noticeable bite, sting, or other discomfort?

Iowa has been covered in a cloud of small gnats right now, and this has got me wondering what the smallest living individual thing that can can cause a medically significant bite. Or even just the smallest thing that can cause anything noticeable on your body.

I'm looking for a single individual animal, while I suppose a single bacterium could get in you and multiply and make you sick, that's not what I'm looking for. I guess something laying a single egg in you that grows into something might count though.
posted by cirrostratus to Science & Nature (15 answers total) 4 users marked this as a favorite
Here in the south, we have chiggers. They are microscopic and can't be seen with the human eye. Wikipedia says 1/60th of an inch.
posted by raisingsand at 11:53 AM on July 3, 2013 [6 favorites]

OMG noseeums gave me some of the worst bites I've ever had: itchy blisters that lasted nearly a month. I believe they got me near a stagnant puddle at a campsite on Oregon's Rogue River. And no, I never saw them.
posted by ottereroticist at 12:01 PM on July 3, 2013 [1 favorite]

Irukandji jellyfish? Their bells are usually just 1/4" to 1/2" wide, and all but invisible in the water. Here is a photo.
posted by divined by radio at 12:33 PM on July 3, 2013

Scabies are small and pretty irritating.
posted by BenPens at 1:06 PM on July 3, 2013

Would a virus count in your equation of "living thing?" They don't bite, per se, but certainly inject genetic material into cells.
posted by Cool Papa Bell at 1:08 PM on July 3, 2013

More common where I am, bed bugs. The baby ones can be as small as 1.3mm, which the internet tells me is ~1/20". Their bites itch like crazy and they don't go away.
posted by ethidda at 1:24 PM on July 3, 2013

You can certainly see chiggers with the naked eye. 1/60th of an inch is 4/10 of a millimeter. The periods at the end of these sentences on your screen are probably about that size. Chigger larvae, which do the biting, are smaller: 1/150th of an inch or about .17 millimeters, about half the size of those periods, but still visible.
posted by beagle at 1:31 PM on July 3, 2013 [1 favorite]

Scabies is not a critter, but an infection caused by mites, which are tiny arthropods.
Swimmer's itch is a rash caused by a tiny fluke, which tries to burrow into your bloodstream as it does with ducks, but it dies in the process, causing an itchy reaction.
If you dry yourself off well after swimming in infested waters, you won't have a problem.
posted by weapons-grade pandemonium at 1:35 PM on July 3, 2013

Response by poster: A virus isn't what I'm looking for here because it isn't the individual virus that makes you sick, it isn't until it reproduces into many viruses that you get sick.

Chigger larva seem like the smallest things so far. What about lice and scabies, does a single louse bite itch or do you need to get a good colony going before they're noticeable?
posted by cirrostratus at 1:35 PM on July 3, 2013

There's a theory that some people's rosacea symptoms are caused by demodex mites that live in or near hair follicles. This would fall into your 'other discomfort' category, though—the mites don't bite you, but they do have a short lifespan, and it's thought that the bacteria in their faeces/decomposing bodies causes irritation. Demodex mites can also cause mange.
posted by EXISTENZ IS PAUSED at 3:29 PM on July 3, 2013 [1 favorite]

We encountered no-see-ums, aka cedar gnats, biting midges, midgies, sand gnats, etc, in southern Utah. They are quite horrible.

They are larger than chiggers, measuring about 1-4 mm, so they are not really invisible per se, just rather small. A distinguishing feature, however, is that they are small enough to go through ordinary window screening material. You can get netting/mesh with smaller openings that is designed to keep out no-see-ums.

An interesting article telling all about them here.
posted by flug at 3:50 PM on July 3, 2013

Adding to the above--three things that are quite small and can bite humans:
  • Ticks - the larva are be about 1/64 of an inch in length, though I don't know if they bite humans in the larval stage. Other stages are somewhat larger. I can say from personal experience that some ticks are small enough to be quite difficult to see.
  • Mites - some types of mites do actually bite humans, though my impression from reading the linked articles is the human-biting types are larger--not microscopic like some mites, but more like 1/64 of an inch or so.
  • Thrips - most are about 1mm in length but some are as small as 0.5mm. Some varieties do bite humans.

posted by flug at 8:56 PM on July 3, 2013

I vote for chigger larvae as the biggest discomfort to size ratio of any insect.
posted by RobotVoodooPower at 6:30 AM on July 4, 2013

Scabies mites don't have itchy/painful/noticeable bites, the itch is from an allergic reaction that you develop over a longer exposure to the mites (which burrow under your skin, lovely). One of the reasons why they spread so nicely, you don't know you're infested until about the six week mark.

That said, if you have enough exposure to start triggering the allergic reaction (even exposure a long time ago), a single mite burrow can be incredibly itchy and noticeable.
posted by anaelith at 8:10 AM on July 4, 2013

Oh, sweet lord this thread is making me itch... My run-in with no-see-ums was back in the late 90s. We lived in a 2nd floor apartment and I had a fan running in the window because it was the middle of summer. Over a period of weeks, I kept getting bitten on the arms but I could never see what was biting me. I started to feel paranoid and every time I got bitten I would look around frantically, only to find nothing. It went on for so long and that I thought I might be losing my mind.

Then, one day, I was fast enough to squish the thing that had bitten me and after doing a little research on the net it turned out to be a biting midge. They'd been breeding on the ground floor due to the landlord letting the hose continuously drip after he'd used it, and this created a small pool where they were breeding. Then they'd float around in their evil little midge-cloud until they got high enough that the fan would suck them in through the screen (yes, they're that small). At which point, they were free to flit around biting the ever-loving crap out of me and making me question my own sanity.

My solution was to put the fan in the other window and leave the problem window closed for the rest of the summer. It worked and I've been midge-free and mostly sane ever since.
posted by Arrrgyle at 10:27 AM on July 4, 2013

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