Masses of black mites with red legs – Clover mites

2011 March 12

We have a large boulder in the front yard that the girls and I like to play on (Sandy bought it for me on my birthday a couple of years ago. She got it at the gravel pit in Hancock. It’s about 6 feet in diameter. I’m very fond of it). It is gradually weathering away, and pieces of it flake off from time to time. A pretty large piece flaked off on September 5, 2010. This exposed hundreds of tiny red-orange eggs (each only about a quarter of a millimeter across) that had been laid in the crevice underneath the flake[1]:

So, eggs. Hard to identify until they hatch, and these had evidently been laid to overwinter and so probably weren’t going to hatch until spring (and, now that they were exposed, probably weren’t going to survive the winter in any case). But, given the tiny size, the best bet was that they were some sort of mite eggs. And the large numbers suggested that whatever had laid them was fantastically common.

My first impulse was to figure, well, I’ve accumulated a bunch of mite photos by now, maybe I should just run these along with actual mites as part of an “Unidentifiable Mite” issue, and clear out some backlog. So I decided to start with these guys, that Sam had found absolutely covering a small rock back on May 31, 2010:

But then, while prepping the photos, I saw that mixed in with the mites (who were about a millimeter long), there were also a number of tiny orange-red eggs.

Oh, sure, it’s circumstantial evidence that probably wouldn’t get a conviction in court, but it’s good enough for me. These mites do seem to go with those eggs. So now I feel like I’m on a roll, and maybe the mites can actually be identified, tying the whole thing up into a nice, neat package and making this whole posting about just one kind of mite after all. Looking at the mites a bit closer, and in spite of the blurriness from blowing up the pictures so much, we see that they have brownish-black bodies, orange-red legs, and the first two legs are much longer than the others:

So, this isn’t much, but is it enough for an ID? After running a google search on “mite, black body, red legs”, and rummaging a bit, it turns out the answer is evidently “Yes!”

These look to be Clover Mites, Bryobia praetiosa. At least, several sites that I’m finding have pictures that are a close match, but Wikipedia (and a few others) show Bryobia praetiosa as being orange mites, and not black mites with orange legs like mine. Maybe there are two color phases. Or maybe Wikipedia is wrong. Or maybe I am. Any of these is quite possible. If this is what they are, then the are evidently one of those species where the females are parthenogenic and there are no males, so they can lay lots and lots and lots of eggs without spending any time on the whole “mating” business.

Anyway, Clover Mites are evidently pests in two ways. First, they live on plant juices, and if they are especially numerous they can damage clover and discolor grass in lawns. Basically giving you a mild case of “lawn mange”[2], although if the lawn is looked after well their effects generally aren’t too noticeable. Second, they are yet another species that forms hibernation aggregations in the winter, and so they tend to move into houses in numbers given a chance. Being so small, they can easily get through window screens and small crevices. They don’t do any actual harm indoors, though, and so they can simply be vacuumed up. They should not be crushed, because they leave red stains on whatever surface they are crushed on.

And, they look like they are related to velvet mites, and so probably taste horrible. Just in case you were tempted to eat them.

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[1] There’s also some other small brown arthropod off to the right of the eggs. I don’t know what it is. I suspect it is some kind of very small “true bug”, but it might be something else entirely.

[2] “Mange” is a general term for skin diseases caused by parasitic mites, mostly in mammals. They look kind of like this, only smaller[3]:

The pictures I’ve seen of lawns damaged by clover mites show thinning and bare spots, which is kind of like what happens to the hair in, say, dogs with mange.

[3] That’s the “mange” or “scabies”[4] mite (Sarcoptes scabei) from Giant Microbes. Sam and Rosie also have an E. coli; a “stomach ache” (Shigella), a “sea sparkle” (Noctiluca), and a “red tide” (Alexandrium tamarense). The stuff at Giant Microbes mostly looks like quite accurate replicas of the real things, aside from the eyes.

[4] It’s evidently called “scabies” when humans get it, and “mange” when some other animal gets it. Because we’re special, that’s why. It does appear to generally be a different subspecies of mite for each animal, but humans can get at least one kind of mange[5] from dogs, and dogs probably could get scabies from us. But still, it seems to me that mange is mange, and we should call it what it is rather than inventing a new name so that we can delude ourselves into thinking that we don’t share diseases with dogs.

[5] There are at least two kinds of mange that dogs get, caused by different kinds of mites. The kind I’ve been talking about (the contagious kind) is “sarcoptic mange”. The other kind, “demodectic mange” or “red mange”, is caused by the mite Demodex canis, which pretty much all dogs have in their hair follicles but that generally don’t cause any symptoms. But, if the dog gets old, sick, or otherwise has a compromised immune system the mites can get out of hand and cause obvious hair loss and skin disease.

7 Responses leave one →
  1. March 12, 2011

    Here’s a bit of mite anatomy for you. A quote:

    “I was not surprised to find out that the mite had a brain since it seems pretty smart about seeking out hosts. (Though its location below the esophagus is a bit strange.) In fact it has a reasonably well-developed central nervous system that has “allowed for the evolution of complex behavior” (Audesirk et al 2008). There are different sensory structures on the body surface that are important since they have no eyes (Nixon 2007). The most common are hair-like setae. This mite has a group of them on the upper part of the tarsus of the first leg that function as an olfactory organ (Savory 1964). ”

    I would think that mite behavior would be something you could accurately model with some relatively simple neural networks. A quick search revealed this

    “A group of ethologists — animal behaviorists — have demonstrated that these mites migrate through our homes in crowds. They like the occasional communal road trip, and they follow each other using some signal, perhaps chemical, to chose the route more traveled.”

    Wow! You can herd mites! I wonder if mite-herders have federally-funded poetry recitals just like cowboys.

  2. March 12, 2011

    A link is on the way, along with some poetry. :-)

  3. mike permalink
    January 17, 2012

    i have just found 3 of these mites on a pice of paper outside on the side of the road when i was walking that was the first time i have ever seen this kind of mite and what can really kill mites because i have this mite killing stuff but it does not work i can spray it on them and they still walk around the stuff is called (organica ready to use k+neem) plus the stuff smells like rotten-pee it cant even kill a fruit-fly so please someone email me back thanks.

  4. January 17, 2012

    Mike:

    From what I can see online, “Organica ready-to-use K+Neem” is mainly just the potassium salt of fatty acids extracted from “neem oil”. This does not strike me as a particularly effective insecticide. Neem oil does not appear to be an insecticide as such, it is more of a repellent. I would expect it to drive certain insects away, but not to kill them.

    I’m not sure what specifically would be used to kill these mites, but on the other hand I’m not sure why you want to. They might stunt your grass a bit when present in very large numbers, but three of them on a piece of paper is hardly large numbers. Personally, I’d recommend ignoring them.

  5. Ian Salloom permalink
    April 26, 2012

    Look to be Spruce spider mites. They generally have a dark brown/ olive color. But i think you have pics of 2 different types mites. Also I’m way more interested in the lichen looking spider to the right on the first pic.

  6. April 27, 2012

    Ian:

    While the Spruce Spider Mites do look generally similar, they are normally found in or around their host trees. These were found on rocks in the lawn, which I think is much more typical of the clover mites.

    As for the camouflaged arthropod on the right in the first picture, I’d kind of like to know what it was, too. Unfortunately, I didn’t notice it while I was taking the pictures of the eggs (camouflage, right?) so I only have the one photo including it. Which isn’t good enough for any sort of ID.

  7. Ian Salloom permalink
    April 29, 2012

    Tim:

    I agree with your statement of clover mites typically being found in that area. But as with any insect there are always exceptions. I have recently treated a home that had both clover and spruce mites all over the south and east wall of the home. I can only assume they were there for the heat from the sun. Possibly these mites were doing the same on that rock? I did find a few sources that state the clover mite may range in color from orange to black, but none of those sources were what I would consider to be a credible source.

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