Christmas stocking animal

"In the blink of an eye..." The phrase is used to suggest speed, and with reason; the human eye can complete a blink in 0.15 seconds, or 150 milliseconds.  Fast enough; anything that happens faster than that, we fail to notice.

A springtail's response time is about one tenth of that. In 18 milliseconds, less than 0.02 seconds, he has disappeared from here and landed over there, up to 100 times his body length away. And he arrives in the new location primed and ready to leap again, should the situation not be to his liking; he has no steering mechanism and has to take potluck. His continued survival depends on being able to move on instantly.

He has no wings. His legs are slender and used for walking. For those high jumps, he uses a spring and lock system on the underside of his abdomen. The furca, visible as he jumps, is a pronged, clawed fork, hinged near the tail. Usually, this is carried folded up, ending just under his chin, and secured by a locking mechanism, the retinaculum. When the lock is released, the fork snaps back like the drawn string of a bow and arrow, flinging the owner into the air with great force.

Globular springtail, caught mid-leap.

Quite simple, really. Easily understood. Except that it takes considerable energy either to leap, or to re-set the spring. So I looked closely at the underbelly of the springtail walking up the glass wall of the spider box.

View from the tail end.

Yesterday's photo, again.

The spring is that long V up the center. Between the two prongs, about mid-way up, there is a small button; this is the lock. But what are all those other contraptions?

I found a couple of very helpful photos on Flickr, here and here, annotated by Frans Janssens, the go-to Collembola expert. The large round organs on either side of the base of the furca are torsion bars, the spring mechanism. (I had to look this up; it's been a while since I studied these.

A spring can be defined to be an elastic member which exerts a resisting force when its shape is changed due to an applied force and returns to its original shape when the force is let off. ... when one side is fixed to an immovable object and the other is twisted, torque is applied. The torsion bar resists this torque and like any other spring it returns to its original position when the torque is let off. From a GM truck site.) 

The bars are powered by large muscles in this abdominal segment.

Slender springtail, showing the furca and torsion bars.

Now, look at the photo of the leaping springtail again. (Re-inserted below, to save scrolling.) See that thick, protruding bar just below the second set of legs? That's the collophore, or ventral tube, another unique springtail piece of equipment. This is what gives the springtails their scientific name, Collembola, from colla, glue, and embolon, a plug.

Globular springtail, caught mid-leap.

All Collembola have a ventral tube. From this tube they can everse two 'sacs'. In Symphypleona, (the globular springtails) these sacs are evolved into long tubes. These eversible tubes are multifunctional organs. They are used to regulate the internal osmotic pressure by taking up water with the tips of the eversed sacs/tubes. They are also used as an aid to adhere themselves on a smooth substrate surface .... In Symphypleona the long eversible tubes are also used for grooming. (Frans Janssens)

The BugGuide page where I found this shows another use for the tubes; a springtail turned belly-up is trying to use the tubes to right himself. Frans comments, "This is a trick only Collembola can perform."

And how about this one? Here's a photo of a springtail using an eversible tube to drink the dew off his own back! (Collembolas, Jan van Duinen)

We're not done yet! Springtails are full of surprises; Christmas stockings, all lumpy and bumpy with mysterious packages.

Beautiful patterns, no two alike. I love this "Southwestern blanket" one.

Look at the shape of the eyes. Well, not exactly eyes; they're irregluarly shaped eye patches. Each one is dotted with up to 8 "ocelli", simple eye, not joined to each other, and of different sizes. (Image) These are not like the compound eyes of insects and instead, are called "composed eyes". The internal workings are not the same, and the individual eyes never touch each other.

One last photo; Smiley!

Cheerful little jumper, isn't he?

Update: in the comments, "Don't Bug Me" added a pair of links to YouTube clips from a David Attenborough series, "Life in the Undergrowth", showing some great footage of springtails. In the first, as the animals leap, if you watch carefully, you'll see the furca folding back into place while the animal somersaults through the air. The second shows a head-butting mating dance. Thanks, DBM!

Update #2: I just found this video; a BBC team catching and photographing a jumping springtail. Check it out!