Ant Lions: Their Extraordinary and Curious Life

Ant Lion; source: flickr.com

Ant Lions: A Unique Creation of Nature

Kids love ant lions not only because they walk backwards or have one of the most amazing types of housing among the world's insects. Starting from their name, which has a ring of irony and a flight of imagination combined, ant lions, as we see them, are something else, a winged insect in disguise or rather in the making. 

Ant lions are not a single species but the larvae of a group of flying insects, the common factor being the special kind of predatory pattern. In their larval stage, they eat small insects, mainly ants, by trapping them inside a pit they prepare in loose sand- ephemeral construction with great geometric precision. 

This is one of the reasons why ant lion larvae are more popular than ant lion adults, at least among the kids who dig them up from their pits to hold them in their palms and enjoy and feel them walking backwards.

Ant Lion Pits

In our place, as children, we used to feed the ant lions by putting ants into their pits. To watch the hunt was just fun. Only after many years into adulthood did we realise the ant's struggle for life inside an ant lion pit.

The home of the ant lion is a funnel-shaped pit, one to two inches deep and one to three inches in diameter at the rim. The abdomen is the digging tool, and the dug sand is heaped on its roomy head. While digging, sand is thrown off the pit by the quick action of the head. 

Once the pit is ready, the ant lion will stay hidden near the vortex of the pit. Any small insect walking on the rim would fall into the pit only to be devoured by the hiding ant lion. Once the insect realises it is trapped, its instinct will be to try to climb up. 

The slope of the pit and the shooting sand spray in all directions would make this very difficult, if not impossible. At this exact moment, the insect attempts to escape, causing movement in the pit, and the ant lion springs to action. Now, the ant lion knows there is prey in its pit, and it hurls sand using its shovel-shaped jaws. 

The insect might succeed in a number of its attempts to climb to the pit's edge, but the quick and efficient sprays of sand from the vortex will eventually make it slip and fall. In no time, the efficient jaws of the ant lion will grab the insect. Once the ant lion sucks all the juice out of its body, the insect is spitted out.

A Life of No Waste

There are more things than meet the eye in the feeding pattern of an ant lion. Strange, it may seem that an ant lion has no anus. Using its jaws, the ant lion injects strong enzymes into the body of its prey. 

The enzymes turn the insides of the insect into liquid form, and the ant lion sucks it all up using the same jaw. The discarded outer shell of the insect will be weightless so that the next hint of breeze will carry it away from the pit and leave it clean. As an ant lion consumes only liquid food, its physiology does not need it to defecate. 

After two or three years of this fun life inside the pit, the larvae pupate to turn into an ant lion adult fly, and at this stage, it spits out all the waste material accumulated inside its body. A part of this also goes into the building of the pupa.

Architects or Mathematicians?

How do the ant lions build such perfectly funnel-shaped pits? Pit-making begins when an ant lion draws a circle in the sand. Then, it starts to walk along the circumference backwards. As it goes, it will hurl out small pinches of sand to the outside of the circle using its head. It uses its abdomen to plough the sand and then heaps the sand particles on its head so that it can throw them away. It takes almost 20 to 25 minutes to complete the pit.

How does the ant lion know how deep the sand is when it draws the circle? What if it draws a bigger circle and then finds the sand not deep enough to go down to the corresponding depth of the circle? Won’t that leave the pit incomplete? It is another superb craftsmanship of nature that such a thing never happens. 

The scientific reason behind this is that as an ant lion goes digging, the digging grove is constantly shifting inwards. Hence, the circumference shrinks continuously if the sand depth is insufficient. 

Grzimek’s Animal Life Encyclopedia says that the circle circumference is proportionate to how hungry the larva is. Another research paper says the “trajectory angle” in which an ant lion throws sand particles out while making the pit is 45 degrees. It is also hypothesised that this trajectory angle helps the ant lion to remove the largest particles as far away as possible from the pit and reduce the risk of them falling back into the pit. 

Sedentary yet Smart

Even when prey is scarce, the ant lions usually do not shift their pits. The shifting process is more taxing on their energy reserves than waiting a little more for the next prey to come. However, there is evidence that they can learn to catch the prey more efficiently and in less time, based on the environmental changes around, for example, an abundance of prey. This is important because having more food in a short period allows it to enter the pupa stage fast, resulting in a more prolonged adult life span.

Moon, Rhymes, and the Ant Lion

Let me give you one more beautiful fact from the life of an ant lion. They dig larger pits if they are digging under a full moon. Why so is a question yet unanswered. Also called doodlebugs, the ant lions have always evoked amusement in children in many cultures. A few funny childhood rhymes from around the world involve ant lions. Here are two examples, the first from The Adventures of Tom Sawyer by Mark Twain:

“Doodlebug, Doodlebug, Tell me what I want to know”.

The second one is on the lips of many an English-speaking kid even now, though most of them nowadays live in crowded cities and urbanisation has disappeared most of the ant lion pits:

"Doodlebug, doodlebug, come out of your hole.

Your house is on fire; your children are alone."

These tiny creatures indeed make the planet a more fun-loving place.

References

Ross, P., Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, https://www.marefa.org/images/e/ea/Piper_Extraordinary_Animals-An_Encyclopedia_.pdf

Antlion, Encyclopedia Britannica, https://www.britannica.com/animal/antlion

Tuculescu, R., Topoff, H. and Wolfe, S., 1975, Mechanisms of pit construction by Antlion larvae, Annals of the Entomological Society of America, 68 (4), https://academic.oup.com/aesa/article-abstract/68/4/719/22197?redirectedFrom=PDF

Grzimek’s Animal Life Encyclopedia: Insects, 2003, M. Hutchins et al. (Eds.), Michigan: Gale Research Inc.

Lucas, J.R., 1982, The biophysics of pit construction by antlion larvae (Myrmeleon, Neuroptera), Animal Behavior, 30 (3), pp.651-652.

Hollis et al., Specialized learning in Antlions (Neuroptera: Myrmeleontidae), pit-digging predators, shortens vulnerable larval stage, PLOS, http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0017958.