I am not making this up – well, mostly not.
On the surface of a distant moon, a lone space traveler steps away from his companions and approaches the edge of a large pit. It appears nearly round with no crater wall. He approaches the edge carefully. Then suddenly the lip slides-out beneath him, and he rolls down the side tumbling towards the apex of the cone shaped pit. All he can call out in his soft Texas drawl is, “reminds me of a doodlebug hole”.
I exaggerate, no astronaut fell into a pit, nor was one paralyzed and devoured by an extraterrestrial Antlion. But a similar discussion took place on 24 April 1972 during the third “extra vehicular activity” (EVA) by the crew of Apollo 16 while exploring the surface of our moon in their “Moon Buggy”.
The discussion of the doodlebug took place 240,000 miles from the closest doodlebug as Astronaut Charles Duke described a part of his childhood in the southern United States to the folks at Mission Control.
When I grew up in rural North Carolina, doodling Antlions, also known as doodlebugs, was part of what we did. We did not have a TV. We played outside and ran to the river and splashed and played in it and ran back. On our way up and down that dusty lane, we might see that dimple in the sandy ground of an Antlion’s nest. We generally called them doodlebugs, and we sought to bring them out of their hiding at the bottom of their conical pit. We would disturb the side of the pit gently with a bit of pine straw to see if we could bring the tiny beast out from his hiding place at the bottom of his trap.
These tiny larvae are ferocious looking with jaws nearly half as long as their body, with sharp fangs for grabbing and devouring their prey.
My attention was recently turned to Antlions by an article in Science News which described a study of the Antlion behavior of “throwing sand” upwards from the bottom of its pit. The Antlion of the southern United States is the larval form of Glenurus spp of the family Myrmeleontidea. This family designation is explained by Barb Ogg on the website of the Nebraska Extension Service at the University of Nebraska-Lincoln. “The Antlion family, Myrmeleontidae, literally means Antlion family (myrme = ant) + (leon = lion) + (idae = family). Antlions belong to the insect order Neuroptera, most of which are predators.” The designation “spp” means plural or multiple species. A picture of an Antlion is shown below.
The authors of the Antlion paper studied the Antlion behavior of throwing sand. It was determined that this action is useful in maintaining the correct geometry of the trap the Antlion digs as well as aiding the Antlion in capture of its prey.
The Antlions trap or “pit” is dug in sandy soil by the tiny beast by using its broad body as a bulldozer and working the sand in ever decreasing diameter circles as it moves backwards until the pit is dug. The pit is an inverted cone. The Antlion buries itself at the center of its pit and waits for its dinner to walk in.
Antlion behavior has been observed by countless generations of children who live in areas with sandy soil and also by the adults that the children grew into. After digging its pit the Antlion will lie in wait for its dinner. When a small insect like an ant enters the pit, the sand on the slope of the pit will often give way and slide, with the insect, down to where the Antlion may capture it. However, not just any angle for the slope of the pit will suffice. The trap needs to be constructed so the sides are inclined downwards at an unstable angle. This angle is technically discussed as the “angle of repose” of the soil. A slope less than the angle of repose is flatter and stable and will not shift except under significant pressure. However, a slope greater than the angle of repose is unstable. This means that as a tiny insect like an ant tries to crawl out of the pit, the unstable sand will slip and slide towards the bottom of the pit.
When the Antlion notices the vibration of the ant’s footsteps and the vibration of the falling sand, the Antlion will begin to fling the sand from the bottom of the pit up onto the sides of the downward slope. As described in the study, this produces two results. The prey becomes confused due the torrent of sand falling on it and will be more likely to tumble into the center of the pit. Second, the sand being flung by the Antlion by flipping its head like a shovel, removes the sand that has fallen into the pit and throws it onto the sides of the pit to maintain an unstable configuration of the slope. By these actions as the Antlion’s dinner is tumbling downward, the trap is being set for another insect.
According to the article by Barb Ogg, as well as other articles, these tiny insects do not bite humans nor do they damage plants, so they may be left alone.
I have heard that Antlions respond to singing or chanting a ditty such as “Doodlebug, doodlebug, come out and play”. As fun as this might be there is no proof of its efficacy. However the vibrations of our voice may dislodge sand on the unstable sides of the pit causing the Antlion to investigate the event.
The NASA transmission of the EVA (extra vehicular activity) may be found at https://www.hq.nasa.gov/alsj/a16/a16a1690707.mp3. At time 0:58 Astronaut Clark refers to the structure on the moon’s surface as a “doodlebug hole”. It starts out rather loud and you may want to turn it down. In the discussion, the depression is referred to as an endogenic crater. An endogenic crater is a pit formed by processes beneath the soil surface like a gas bubble moving outwards and erupting through the upper soil layer, or perhaps like a sinkhole. It is not an impact crater.
The transcription of the .mp3, plus other transmissions not recorded in the transmission, may be found at Return to the LM (nasa.gov) starting at the entry for 169:07:53 and going through 169:08:25. The transcription of the conversation contains more information of what was said than the .mp3 recording. Perhaps it was on a separate channel.
The Science News article may be found at https://www.sciencemag.org/news/2020/12/how-voracious-antlions-engineer-deadly-sand-traps. To read the article may require a subscription or permission.
The referenced study of Antlion behavior may be found at Sand throwing in a pit-building Antlion larva from a soil mechanical perspective | bioRxiv .
The article by Barb Ogg on he University of Nebraska-Lincoln may be found at Antlions: Amazingly Adapted Predators | Nebraska Extension: Community Environment | Nebraska (unl.edu) .
A video of an Antlion digging his pit may be found at https://www.youtube.com/watch?v=-AT0J8cBS-U. Watch carefully. You can see the tiny creature throwing sand onto the sides of its pit.
This article’s Title refers to the tale by Edgar Allan Poe, which is a tale of another conundrum.
Copyright (c) Albert Johnson 2021