The Antlion “King of the sand dunes.”

This is a story about crafty fearsome lions, and no, not the kind that sends shivers up your spine when it roars… This kind of lion goes unnoticed by most…. THE ANTLION (family Myrmeleontidae).

The ant-lion is a predator, particularly in the larval stage (pictured above) which can be found in warm regions around the world. The ant-lion larvae “eats” small arthropods, mainly ants, while the adults of some species eat small pollen and nectar, while others are predators of small arthropods in the adult stage too.
The ant-lion larva is a ferocious-appearing creature with a robust body, a very plump abdomen, and the thorax bearing three pairs of walking legs. The pro-thorax (section between the head and the abdomen) forms a slender, mobile “neck” for the large, square, flattened head, which bears an enormous pair of sickle like jaws or tusks with several sharp, hollow projections, these act like hypodermic needles, grabbing prey and delivering a potent polypeptide poison, more than 100 times as effective as a Japanese puffer fish.
The ingenious way in which these crafty predators catch their prey is unique in the animal kingdom. They construct a conical pit trap (depicted below).

When it starts digging a new pit, it slowly moves round and round, flicking sand away from the pit by using its tusks and mid legs, while it uses its powerful back legs to dig into the sand.
The pit gradually gets deeper and deeper, until the slope angle reaches the critical 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.
When an unlucky ant wanders unknowingly into the pit and tries to escape the ant-lion pummels the prey with sand. By throwing up loose sand from the bottom of the pit, the larva also undermines the sides of the pit, causing them to collapse and bring the prey with them. Thus it does not matter whether the larva actually strikes the prey with the sand showers. So in other words… no matter what the ant does it’s doomed to slide back into the jaws of death.

As mentioned above the projections in the jaws of the larva are hollow and through this the larva will suck the fluids out of its victim. After the contents are consumed, the dry carcass is flicked out of the pit. The larva readies the pit once again by throwing out collapsed material from the centre, steepening the pit walls to the angle of repose once again.
The sand has to be just right, fine grained and soft, for this crafty critter to make catching a meal a “slam dunk”
Another interesting feature that makes the ant-lion larvae unusual among the insects is that they lack an anus!!! All the metabolic waste that is generated during the larval stage is stored and is eventually emitted as “meconium” near the end of its pupal stage. This is an important feature; otherwise the ants would be able to smell the predator in waiting and would never fall victim to the ant-lion.
When the ant-lion has eaten its fill (after the larval stage for up to 3 years) the ant-lion will spin a cocoon made of sand stuck together with fine silk spun from a slender spinneret at the posterior end of the body under the sand and pupate into the adult form. These cocoons may be buried several centimetres deep in the sand. It remains there for one month, until the completion of the transformation into the sexually mature insect, which then emerges from the case, leaving the pupal integument behind, and climbs to the surface.
After about 20 minutes the adult’s wings are fully opened and it will fly off in search of a mate. The mature ant-lion (sometimes called a lacewing) has four wings that under a microscope resemble stained glass.
Although (as mention in the introduction paragraph) it has sharp mandibles and big eyes the adult ant-lion (see pictures below) eats only pollen and nectar during its short life, while it superficially resembles dragonflies or damselflies, they belong to an entirely different infraclass among the winged insects. Ant-lions are easily distinguished from damselflies by their prominent, apically clubbed antennae which are about as long as head and thorax combined.

They also are very feeble fliers and are normally found fluttering about in the night, in search of a mate. After mating has taken place the pregnant female will lay her eggs in the sand or on a leaf.

The larval ant-lion might be a heck of a lot smaller than its name sake, but it is every bit the veracious predator.

Riaan Bezuidenhout – Kapama River lodge
16/03/2013

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