6 March 2013

Antlions: the truth behind Star Wars

Anyone who has ever seen The Return of the Jedi will be familiar with Luke Skywalker’s and Han Solo’s plight as Jabba the Hutt attempts to feed them to the sarlacc, which lurks in the bottom of the Great Pit of Carkoon. What might surprise you though is this isn’t far from the truth and many insects live in very real danger of coming face-to-face with such a creature, which is known as the antlion. 

As their comparison to the fictitious sarlacc suggests, antlions are ambush predators and are fairly common worldwide. In fact, they are found in almost every dry, arid environment and around 2, 000 species have been described so far that belong to the family Myrmeleontidae. Like many insects, antlions have a complex life cycle and pass through a larval form before they finally mature into adults. Due to this, the term ‘antlion’ is usually reserved to the larval form of the insect (which are sometimes called doodlebugs due to the spiralling trails they leave in sand while looking for a suitable place to build their trap), as an quick way to identify the form of the insect. 

Just like the sarlacc is, antlions are terrors and are capable of eating almost any arthropod that is unlucky enough to fall into one of their traps. Thus, their diet consists of a variety of insects that ranges from ants (obviously) and termites to small spiders! How their prey is caught however, depends on the exact species of antlion and their surrounding habitat, meaning that they could be lurking in foliage, hiding in the cracks in rocks and bark or be waiting in especially dug pits. 

Unusually among insects, antlions lack an anus and store all of their waste inside their bodies until they undergo metamorphosis (where it is discarded with the remnants of their cocoon).

It is the species that dig pitfall traps in sand that are particularly renowned however, and much research has been carried out into their trap-building behaviour. Typically, antlion pitfall traps are about 3 inches wide, 2 inches deep and are dug in finely grained, loosely packed sand. This criteria allows an antlion to create a steep, treacherous pitfall that their prey struggle to escape from once they've fallen into it as the walls crumble beneath their feet. To make their escape even harder, the antlion will then toss sand at the struggling insect to create a mini ‘landslide’ that helps to drag the struggling insect further into the hole. 

And once the insect has reached the bottom of the pit, it's all but game over and the antlion grabs it in its powerful mandibles, injecting deadly toxins and acids into its prey via several long spines that project from its hollow jaws. The antlion, which is firmly anchored in its trap by forward-facing bristles on its legs and body (that prevent it being dislodged and pulled from the pit), then holds its prey still until it has died and sucks the fluid ‘mush’ from the insect - feeding in same grotesque manner as spiders do. And, once the antlion is full, it throws the withered husk of its prey from its trap in the same way as it tosses sand and sets about repairing its walls. 

Antlions can remain in this larval form for up to 3 years, depending of course on the exact species and the amount of prey that is available, before they encase themselves in a cocoon of silk underground. Here, antlions undergo a remarkable process called metamorphosis where they change into their large, adult form over the period of about a month. Once their transformation has finished, the insects emerge from the ground, wait for their bodies to dry out and harden, and take to the air in search of mates.

Depending on the species, antlion damselflies can vary from being fairly small with 2cm wingspans to being much larger with wingspans of 15cm! Adults are much bigger than the larval form and show the greatest difference in size in any holometabolous insect (one that completely changes form via metamorphosis).

Adult antlions are sometimes are sometimes called antlion damselflies (despite having no relation to the damselfly family), and, depending on the species, vary between remaining as fierce predators or switch their diet to eat pollen and nectar. As their nickname suggests, the adult form look similar to damselflies although they can easily be identified by their extremely long, clubbed antennae and very narrow wings. 

Oddly, antlion damselflies are rarely seen in nature because they are usually active in the late evening and are poor flyers so (rather ironically), are very vulnerable to predators. They can be a real nuisance in desert areas however, where they are more abundant, as they tend to swarm and can deliver a mildly painful bite to any humans that they land on!

So, you might agree then that antlions are interesting insects in their own rights - being such fierce and efficient predators - but, considering they are the inspiration behind one of Star Wars' most famous aliens, they become even cooler and are definitely well worth knowing about!

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