Pleistocene Ant Lions (Myrmeleontadae sp.)

Ant lion pits line the bare soil areas next to the back wall of my house. Ant lions, as the name suggests, prey on ants, though they will eat anything small enough to become trapped in their pits. The larval stage of most species is the monster hidden just below the sand of the bottom of the pit. When an ant lion larva senses an ant walking near the edge of the pit, it flicks sand at the ant, knocking the ant into the side of the pit. The action of flicking sand destabilizes the wall of the pit, forcing the ant to fall within the reach of the ant lion’s jaws. The ant lion then injects venom and devours the ant, or rather sucks the juices out of it. Ant lion larva can live for years without eating and during winter they dig deeper down to avoid frosts. But after they’ve had a meal, they go into a cocoon stage before emerging as adults. They survive on nectar for energy in their brief adult stage spent searching for mates. Fertilized females lay eggs in sand and the cycle begins again.

Some species of flies lay their eggs in abandoned ant lion pits, and their larva use the same strategy as ant lion larva. At least 1 species of parasitic wasp allows itself to be captured. It stings the ant lion larva and lays on egg on it, thus turning predator into prey.

Ant lion adult and larva. Image from below reference. The larva prey on ants and other small arthropods.
Ant lion pits next to the side of my house. Ant lions prefer sandy soil and are common in arid environments. They likely were abundant in the southeast during Ice Ages when the climate was dry and bare soil environments predominated.

There are about 2000 species of ant lions, and there are species on every continent except Antarctica. Their closest living relatives are owl flies and lace wings. They are most common in tropical dry climates, but they thrive anywhere they can find a sandy substrate. I hypothesize they were abundant in southeastern North America during Ice Ages when arid climates prevailed, resulting in vast landscapes with sparse vegetation. Pleistocene climate changes likely increased species diversification when populations became isolated from each other during wetter climate phases that turned sandy environments into isolated refuges.

Ant lions are rare in the fossil record. Ant Lions have been found in 99 million year old amber at a site located in Burma. Scientists think ant lions first evolved about 150 million years ago, so they lived under the feet of dinosaurs. There are no dinosaurs in my yard (unless one includes birds), but their contemporaries live right up next to my house.

Reference:

Badano, D.; M. Engel, P. Basso, B. Wang, P. Cerretti

“Diverse Cretaceous Larvae Reveal the Evolutionary and Behavioral History of Ant Lions and Lace Wings”

Nature Communications (9) 257 August 2018

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