Monday, September 14, 2009

Only the Jaws Project Above the Surface

Ant lions make pits of loose sand, so that anything on the edge slips into the den of the ant lion. Strictly speaking, these are traps. Ant lions eat ants, and so their name. When they're through, they hulk the husks of the carcasses up, out, and over the edge of their pits.

And ants bury their dead.

Picture a pit with ant carcasses around the perimeter and an ant comes along, planning to bury his dead. He goes to edge to collect, and now he himself slips into the den. The ant lion hardly moves; all of his business is done underground, in the dark, at the leisure of the world.

An average-sized larva digs a pit about 2 inches deep and 3 inches wide at the edge. This behavior has also evolved in a family of flies, the Vermileonidae, whose larvae dig the same sort of pit to feed on ants. Having marked out the chosen site by a circular groove, the antlion larva starts to crawl backwards, using its abdomen as a plough to shovel up the soil. By the aid of one front leg it places consecutive heaps of loosened particles upon its head, then with a smart jerk throws each little pile clear of the scene of operations. Proceeding thus it gradually works its way from the circumference towards the center. As it slowly moves round and round, the pit gradually gets deeper and deeper, until the slope angle reaches the angle of repose (that is, the steepest angle the sand can maintain, where it is on the verge of collapse from slight disturbance). When the pit is completed, the larva settles down at the bottom, buried in the soil with only the jaws projecting above the surface, often in a wide-opened position on either side of the very tip of the cone.

The ground is an open mouth beneath your feet but you're too large to be swallowed. I'd imagined the ant lion would be vicious, like a catfish, waiting to strike in the shadows. But where is this prey going to go? The open mouths just make it obvious, and hugely dark. Such a tiny little hell.

The sensation of it interests me. The change in light and environment all at once, the surprise of the predator who had no idea when to expect this. And the ants. They're tossed around, pelted with sand. Shredded apart, and consumed. All in darkness. And then what's left is tossed up into the light, and it's completely quiet again.

1 comment:

Anonymous said...

Ant lions are cool. I've used them for teaching ecology.

Thanks for posting.