Do you remember as a child finding a small, perfectly-formed conical pit in the sand? And then stirring the bottom of the pit with a straw until the little grey bug popped out? It was quite a strange-looking little thing, which we learned was called an ‘antlion’. The name was obvious to us as we knew it was a voracious predator of ants.
But that’s about all we knew. It did not occur to us that they were insects and therefore had another life in a different form. The antlion is in fact the larva of an adult lacewing. But let’s back up a bit and start again.
Antlions, as mentioned, are insects. They belong to the family of insects called Myrmeleontidae. The name is rooted in the Greek words myrmex (ant) and leon (lion).
The antlion starts life as an egg, laid by a flighted, female adult. The egg hatches into a larva (the antlion). The larvae are grotesque-looking, even by the standards of insects. Their bodies are bulbous and hairy, and their flat heads sit on elongated necks and feature a pair of sickle-shaped mandibles. As is the case with all insects, the larval form is dedicated to eating – in this case mostly ants, but any other insect prey will do.
The antlion has a very sophisticated hunting strategy. It makes a trap in the sand. It starts by scurrying backwards, looking for a suitable spot to dig its death trap. In the process it leaves tracks like ‘doodles’ in the sand – which is why they are sometimes called ‘doodlebugs’.
Once the antlion has located a prime spot in soft, fine sand, it starts to dig (still backwards) in ever-decreasing concentric circles. Its digging is very precise in that it flicks out all the larger grains of sand from the pit by using its pincers and mid legs, while using its powerful back legs to dig into the sand. In fact it assesses the size of every sand grain and discards everything but the finest grains.
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 even a 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.
This is an engineering adaptation acquired over thousands of years of evolution. Fine-grained sand pits with steep sides make the best traps!
The hunter now buries itself at the bottom of the pit and waits. Any ant that wanders over the edge of the pit is doomed. As the ant tries desperately to crawl out of the pit, the fine sand forms a little ‘avalanche’ that slides the ant all the way back to the waiting jaws of the antlion. The crafty little beast assists the downward slide by tossing more sand onto the slope to cause a landslide.
When the hapless ant reaches the bottom of the pit, two deadly pincers snatch the prey and swiftly drag it under the sand. Talk about Jaws! These pincers are more deadly than sharks’ teeth as they have little grooves in them, through which the antlion injects a potent polypeptide poison, more than 100 times as effective as a Japanese puffer fish. It also delivers digestive enzymes which turn the ant’s insides into a smoothie to be slurped up by the voracious predator. The drained ant carcass is flung out of the pit.
When the antlion larva has eaten and grown enough (the time depending on the abundance of prey), it does what all insect larvae do. It spins a little cocoon out of silk and sand. The insect pupates and slowly undergoes that magical rearrangement of cells in the body, known as metamorphosis, to become an adult insect. The adult makes its way out of the sand, inflates its wings and flies away. And is it as grotesque-looking as the larva? No, it’s a beautiful lacewing that resembles a dragonfly.
The lacewing does what most adult insects do – they fly around to find a mate. They may stop briefly for a spot of pollen, but mostly their minds are only on one thing. Once mating has taken place, the female lays her eggs in the sand and the cycle begins once more. Adult lacewings, having fulfilled their role, die after about three weeks.
In the life of an insect procreation is all that matters.
About the Author
Whale Coast Conservation passionately lives by its slogan “Caring for your environment”.
Its small staff and volunteers are dedicated to
- raising community and visitor awareness of the unique, biodiverse natural resources of the Cape Whale Coast region and
- to projects that convert awareness into practical actions that lead towards living sustainably.
WCC ensures expert representation in public participation processes that contribute to environmental and developmental policies and legislation. We monitor regional development; and ensure compliance with legislation and guidelines.
WCC increases general public awareness of sustainability through environmental education, citizen-science research projects, community projects and campaigns.
WCC communicates with its audience through exhibitions, signage, technology demonstrations, workshops, talks, film shows, newsletters and articles.
WCC places emphasis on educating future generations through its Youth Environment Programme (YEP). YEP is offered to 24 schools in its target area with a total of over 10,000 learners.
WCC facilitates schools’ participation in special events such as Earth Day, Walking for Water, Arbor Day and Coastal Clean-ups.
WCC facilitates educator development programmes to improve the capacity of educators to offer informed environmental content in their lessons across all learning streams.