Off The Beaten Path – The Index Eagle June 1997 by Bob Hubbard | The Town of Index Blog

Off The Beaten Path – The Index Eagle June 1997 by Bob Hubbard

This article is from the Index Eagle, June 1997 and authored by Bob Hubbard. He has given us permission to reprint his articles but PLEASE DO NOT PLAGIARIZE. This article may not be reproduced without the express written permission of IndexWa.org and/or Bob Hubbard.
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Sometimes while walking alone, I imagine what it must be like to be as small as a bug, flying along high above the grasses, looking down on them as we humans might look down from an airplane to the forested land beneath it. How much huger a small lot becomes; how incredibly many insect-miles it is to go virtually anywhere. And yet, as the insects are small next to us, so are the mites small, next to insects. If a human mile is roughly 1000 body lengths, and an insect mile and a mite-mile were to be proportionally equivalent, an insect mile for an inch-long bug would be about 83 feet, but a typical mite-mile would only be a couple or three feet long. So when I get tired of imagining grass stalks the size of redwoods, I scale down to mite size and look at them as great green columns the diameter of office buildings whose tops might be a mile or more above their bases, and whose leaves are like ten-lane freeways climbing into the sky.

You have to get right down next to things to see them in even remotely the same scale as the mites might, if they had eyes to do so. For instance, you could hold an alder leaf at arms length and still see most of the insects who are likely to visit it, but you have to get real close to it, and bounce the light off the surface just so to see a mite sitting on it.

But if you want to track down a mite with your naked eye, you might want to start by using a bare rock surface instead of what could turn out to be a whole bunch of leaves. Skimming low over the rock’s surface, you can see vast areas at a glance, as if you were flying over a desert looking for stray cattle in the arroyos. The rock is not unlike a desert; water doesn’t stick around long after a rain, almost nothing grows there, and shade may be nonexistent. The temperature at the surface often climbs well above 120 degrees on sunny days.

Most mites I’ve found in these desert like habitats have been predator mites. Their prey, creatures such as springtails and other mites, must be out there too, but it’s usually the predators I see, probably because they are usually colored a bright red, and their rapid movement catches the eye.

Of all the mites I’ve found this way, most have been from a single family of mites, the Anystidae. This is not an especially diverse family, but its members are widely distributed. In fact, I’d bet that many, if not most of the people reading this have actually seen an Anystid before. Think back: have you ever been reading a newspaper and noticed a small red dot scurrying around on the newsprint? How about when reading a book …ever notice any small scurrying red dots on any of the pages? I have, dozens of times, but then, I’ve been on the lookout for them; once you start looking for them, it’s only a matter of time before you track one down or it tracks you down. These red dots are mites. Anystid mites, more often than not.

Mites are more closely related to spiders than to insects, and if you look at an Anystid through a magnifying glass or microscope you can see the obvious resemblance. Superficially, they look like a shrunken-down version of a long-legged tarantula: most of what you see is their eight hairy legs. But their body only consists of one section, unlike the two-segmented bodies of spiders.

It almost seems a miracle that anything as small as a mite could live and get around; where, for Pete’s sake, in that little dot is there enough room to stuff all the necessary vital organs, and where in those long skinny legs is there room enough for the muscles, blood vessels and nerves necessary to make them work? And how do you coordinate eight legs, each with seven separate musculated sections? However you do it, Anystids do it extremely well; they are such good runners they’ve earned the common name of “Whirligig mites”. In my experience, they are almost constantly running.

It turns out that, while miniaturization poses special mechanical problems, it also allows for some fairly elegant solutions. There’s no need for blood vessels, for instance, in a body so small; the inside of the body and the legs is one big interconnected cavity, and movement keeps the blood sloshing around so that all parts get bathed in it. And then there’s those pipe stem legs: they’ve got fewer muscles operating them than you might expect. Most creatures have a set of muscles to bend their legs and another set to extend them, and walking is a coordinated effort between those opposing sets of muscles. Mites have opposing muscle-pairs in only the first and last segments of their legs; in the other segments there are muscles to curl the legs, or bend the knees, but none to unbend the knees and cause the legs to extend. So what causes leg extension? Hydrostatic pressure.

Have you ever blown up a rubber glove to make a five-fingered balloon? If so, you know that it is the air pressure in the balloon which makes the fingers pop out straight. Bend them and release them, and they will snap back straight again. Mites are a bit like those fingered balloons; they are essentially little sealed bags of fluid with legs appended to them. Further, they have large sets of muscles which loop around their guts and are designed to squeeze them. When their gut muscles are clenched, it increases the internal pressures in the mite, and this pressure is what uncurls the legs and extends them.

When they run down their prey, the Anystids dispatch it with a quick bite from their unusual mouthparts. To visualize these parts at work, imagine that you have a hunting knife held stabbing fashion in your right hand. Cross your right hand over so that its thumb, and the hilt of the knife touches your left shoulder, and the blade is pointing forward. Now imagine the left hand with a similar knife held likewise at the right shoulder. If you were to attack, say, a telephone pole, you could stab it on the left side with your right hand or stab it on the right side with your left hand. Or, you could let fly with both hands at once, which is kind of how the crossed-over, sickle-shaped chehcerae of the Anystids work. Fast-reacting prey like springtails, who can hop the equivalent of a city block when startled, can be securely gripped on the first bite by these tong-action mouthparts. Flanking them is a pair of jointed, fingerlike food manipulators called palps; with Anystids, these are almost half as long as the legs, and may look like an extra pair of legs which lack terminal claws.

Run and stun. Grab and stab. Chop and slop. Slurp and burp. Another culinary pit stop on the great racetrack of an Anystid’s life. But there must be more to life than this, right? Right. There’s finding a mate, for instance. That’s something I’m not sure how they do. Consider the situation of a mature but single Anystid in it’s native environment: a lone dot running like hell across a burning desert of hot rock, somehow hoping to run into another of the same species but opposite sex who’s the right age for breeding and in the mood. Not exactly encouraging odds, but somehow the breed survives; I eagerly await the scientific howdunnit and wonder if it’s been published yet.

Anystids have always been more than just ordinary mites tome. Cleared and mounted on a microscope slide, they are one of the most beautiful of the mites. They are also one of the most difficult mites to make a good slide mount of, because of the way their long legs tend to curl up into a kind of a hopeless looking knot when you drop them into the mounting medium on the slide top and get ready to drop the cover slip over them.

A good, obedient mite specimen will splay its legs out like a starfish, and as the cover slip lowers, it will stay in position. A typical specimen, on the other hand, will sort of surf around on the slide top and end up skewed sideways, sometimes with one or more legs folded up. A typical Anystid specimen, at least for me, has to have each of its legs patiently unfolded, and has to be held firmly yet delicately in place, so that they cannot refold into their beloved “hug-knot” configuration. The word “delicate” seems too coarse to describe the operation.

This manipulation is done with sharp tweezers and needles, while looking through a microscope at the victim, -er, specimen, which, you’ll remember, is about the size of a spot on a Ladybug’s back. Through the lens, the needle and tweezer tips look like telephone poles as they poke, grab and pull at the specimen. At first it looks and feels like some second party is operating the telephone poles by remote control, with all the grace of a blind backhoe operator, but practice improves the game. I’m not the most coordinated of persons, so I practiced on commoner soil mites before I attempted wrestling with an Anystid. I pulled off more arms than a drunken superman at a hand-shaking contest, but I developed a sort of “feel” for dancing these little critters around using pokes, tugs, and judicious use of pressure on the cover slip. And I finally got a good slide of an Anystid. The school has it now. I have my degree, but they have my mite.

I never gave up being a small game hunter, and though I hung up my tweezers a while back I still pack a hand lens into the bush. I still drop down to mite height occasionally, and skim my eyeballs over a hot rock desert looking for predator mites, but really, I have just as good a chance of finding them in a newspaper or on a concrete wall.

I read in a book recently that the Tarahumara Indians of Mexico have running so deeply ingrained in their culture that individuals have been known to cover over 600 miles in a week, barefoot. Even scaled down into mite miles, I have a feeling that for one of the Whirligig mites, that would be a slow week.

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