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Monday, 21 July 2014

Ant lions rule!

This is another retread from a nursery news letter, but I have added more information at the end about catching, keeping and managing these cute little carnivores. Ant lion has a different meaning in other parts of the world, but I gather that there are strong similarities.

Aged seven, I was given a book called Beetles Ahoy! and read about ant lions there and fell in love with them. Family Myrmeleontidae (Neuroptera) to entomologists, these are the larval stage of lacewings. They dig neat holes.

The name is a misnomer: they aren't lions, as anybody can see. More importantly, they don't always eat ants—I have seen one catch and presumably eat, a small weevil.

Any loose material like sand has a natural angle of rest. This is the steepest angle it can hold without tumbling down. Sand dunes, sand heaps and sand banks are all limited by this angle. So are wells dug in creek beds.

This angle shows up in sandstone cliffs which contain fossilised sand banks, and you can see these all over North Head. The best view is from the lookout off the Fairfax Track.

So sand has a position of maximum stability. Ant lions rely on this. They dig conical pits in the sand by burrowing into the sand, and flicking sand up and away with their heads so the sides settle at the angle of rest. Then the predator sits hidden at the bottom, waiting for something to fall in.

Anything going over the edge dislodges sand and tumbles down. As it tries to scramble out the ant lion flicks the fallen sand out. This undermines the side which start to slide down, while some of the flicked sand knocks them down. The prey slides down as well.

Once the unlucky animal reaches the bottom of the slope, the ant lion seizes it in its pincers and starts sucking it dry. In the end, it flicks the empty husk of the prey out of the pit.

They are all over North Head, but you have to know to look for a small conical pit, 1–3 cm across in dry sandy soil. The soil may be close to one of the gum trees that kill grass, inside a hollow tree, along the edge of a building or under a rocky overhang. Sometimes, you can even see ant lion pits, right out in the open.

At times, and for assorted reasons, I keep some as pets. Here is all you need: just add ants—or weevils.

Catching ant lions: if you chase them they can burrow fast.  I use and old cup and scoop up the pit and everything for about 3 cm below the base, and I tip this sand into a jar.

Once i have several of the animals, I transfer the jar's contents to a tray containing about 3 cm of dry, clean sand, sprinkling the sand from the jar over the surface. The ant lions lie very still for a while, so you may not see them. Then they move backwards across the sand before backing down into it. You can see a trail going from left to right in the photo above, half-way up.

They often wait for a day or so before making a pit, so be patient.

Catching ants: Do not use a pooter! Ants release formuc acid when they are handled, and this burns the throat. Depending on the species, put a sheet of paper with a spot of Vegemite 
 or a scrap of meat (for meat ants) or honey (other ants). When enough ants are on the sheet, pick the paper up and shake the ants into a jar.

The rig on the right shows a neat way to stop the food ants escaping.  There is water in the larger tub. In use, the handle on the inner tub is upright, so there is no escape for the ants.

Water: Ant lions live in sandy soil that is somewhat shaded and also protected from direct rain, so they probably don't like full sunlight or damp conditions. I imagine they get all the fluid they need from their prey, but I usually keep one corner of the tray clear of sand, and add small amounts of water in that corner, enough to saturate the lowest millimetre or two of the sand.

When you have finished with your ant lions, release them back where you caught them, or keep feeding them until they mature, change into lacewings and fly away. If you have a covered tray, you may be able to see the adults when they emerge, but check it every day, and don't open it inside.

The photos are all mine, the drawings are from my 1985 book, Exploring the Environment.

Incidentally, it struck me that maybe I was repeating myself, and indeed I am: there are even some pictures in common, but the approaches are a bit different.  Now I wonder: am I getting better or worse?  You decide: the first version is here.

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