I'm reading a book on mushrooms, and the author mentions antlions. They have nothing to do with mushrooms, but it spurred me to google it, since I've been telling visitors "Hey, at the bottom of that sand pit is an antlion, so they tell me." And that was the extent of what I knew.
Google has enlightened me, and now I enlighten you.
Antlions, like many of us, start life as an egg. Unlike many of us, their eggs are laid in loose sand or dirt. They hatch into the larva stage and scuttle about until they find a good patch of loose sand or dirt to dig into. They are about 1/2 a centimeter big (not big, in other words). Their scuttling leaves traces in the sand, and because of that, are also known as doodlebugs.
Very often, you'll find many antlions have chosen the same area of good sand. Here, you'll find a lot of them on trail 3, just past the wood pile by the house.
They dig into the sand, creating the funnel shape. When wandering insects fall in, the antlion grabs them with it's large pincers and inserts juices into the insect which creates a scrumptious antlion smoothie. When the antlion has slurped the last, it throws the insect carcass out. Curiously, I've never seen either doodles or discarded insect carcasses by our antlion dens. Perhaps because, once we see them and say "Oo, what's that? Oh, that's an antlion, so they tell me", we walk right over them, destroying doodles, sand pits, and crushing carcasses to blend into the loose dirt.
The sandpits are about one to two inches across (diameter). Why do wandering insects fall in, you ask? Why don't they simply walk back out, if they find themselves in it? And I might add, why are the traps the size and shape they are? That's where my love of geology, and geology terminology, comes in. Suffer me, please. (Or skip it..)
The slope of the funnel is not based on some aesthetics the larva might possess. Nor on some instinct to build the funnel precisely this wide and this deep. Nope. Rather, the slope is determined by the sand/dirt's angle of repose. (Did you miss it? That's a technical geological term. Angle of repose. Poetic, huh? Makes me envision a naked goddess on a chaise lounge, gazing directly at you.)
Angle of repose is defined at that angle (slope) at which those particular sized particles of sand/dirt/clay at that particular humidity level, etc, are just on the brink of not falling down the slope. So the antlion creates the funnel slope until he can feel the particles are just on the brink of not falling down. This means when an ant comes along, she (for they are always shes) adds just enough energy to make the particles fall down the slope, and the ant goes with them. Very similarly (but not the same) to when when we humans add just enough energy to a loose rock on the trail that it falls further downhill, and we go with it. Thankfully, there are no antlion jaws waiting for us.
(Aside - I also wonder how antlions fare with fireants. Are they able to subdue these invaders? Are their species of antlions where fireants usually lived that can handle them?...)
The larva live in this stage for about three years, which is long for this small a creature. Made longer by the fact that they have no anus. Yup. They store all the unused stuff up, then barf it up in one big pellet before they change to the next phase.
When it's ready, anywhere from 2 to 3 years (when is that? how do they know? do they keep a calendar? when they feel full? when they really, really, REALLY need to poop?) they build a cocoon using the sand and dirt particles around them and silk from a spinerette to bind it all together ("silk" is the word wikipedia uses. Is this convergent evolution with spider silk, or is it a different molecule?). They stay in the cocoon for about one month, and when they emerge into their adult stage, they have completely metamorphized into something resembling a damselfly. Because of this, I'm betting the impetus for the larva to metamorphize is that somehow it senses it's full - that it's got enough molecules, finally, to build an adult body.
And, wiki tells me, the antlion has the largest difference in size between the larva and adult stages - they manage this because the larva stage is a squat, compact, dense thing and the adult stage is built so flimsily and ethereally. A note to fans of transformers and metamorphizing superheroes here: I can totally buy that a dose of radiation can transform a mild mannered scientist into a monstrous creature. But folks, the total mass just gots to remain the same! There are only so many atoms that can be rearranged just so many ways. There's no way a hulk can be produced from Bill Bixby. Unless he was a really short hulk.
As adults, their primary purpose is to find a mate, mate, and for the female to then lay the eggs. They only live about a month in this phase, and they are active at night, so are not likely to be confused with damselflies. One website says they might give you a bite if they land on you. But they aren't trying to eat you - as adults, they eat nectar. Which makes sense - creatures need to eat protein to build their bodies, then sugars and carbs to give energy to the adult bodies they created. Some birds, I believe, also eat like this - adults bring protein food (insects, etc) to the young, who switch to sugars and carbs (seeds, nectar if you're a hummingbird) when they're adults.
Finally, (thank God, you say) google enlightened me to the fact that people keep these things as pets. I.. just.. don't know what to say about that. Watch a funnel for three years, then watch an adult fly around for a few days (if you're lucky).
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