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Antlions Trapping Insects

8-14-14  antlions - 230The larvae of a predaceous group of winged insects (family Myrmeleontidae) that closely resemble dragonflies and damselflies are referred to as “antlions” – they have the ferociousness of a lion and prey mainly on ants. The manner in which an antlion traps its prey is ingenious. It excavates a conical pit in sandy soil (an antlion is also called a “doodlebug” because of the squiggly trails it leaves in the sand looking for just the right spot for a pit). Using its head as a shovel, it tosses out sand as it turns in a circle, digging deeper and deeper, until it forms a pit roughly two inches deep and three inches wide. The antlion lies at the bottom of the pit, covered by a thin layer of sand except for it pincer-like mandibles, which are ready to snatch prey at a second’s notice.

The slope of the sides of the pit is at the angle of repose – as steep as it can be without giving way – so when an ant accidentally steps over the edge of the pit and falls in, the sand beneath it collapses, carrying the ant to the bottom of the pit and into the pincers of the waiting antlion. If the ant tries to scramble up and out of the pit, the antlion tosses a load of sand at the ant, knocking it back down. The antlion then injects venom and digestive fluids into the prey via grooves in its mandibles, and drinks the innards of the ant through these same grooves.

The antlion’s anatomy is as unusual as its method of capturing prey. It has a mouth cavity, but no mouth opening, and no external opening for solid waste. Because digestion takes place outside of its body, the antlion doesn’t accumulate a lot of waste, but what it does accumulate stays inside of it until the antlion matures into an adult. This can be anywhere from one to three years, depending on the species. When fully developed, the antlion constructs a small, round pupal case out of silk and sand, in which it overwinters. It emerges from this case the following spring as a winged adult. (Thanks to Joan Waltermire and John Douglas for photo op.)

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7 responses

  1. Jean Harrison

    No mouth, no anus? That’s amazing for a complex animal.

    August 14, 2014 at 1:31 pm

  2. Kathie Fiveash

    I’m echoing Jean. This is fascinating. I’ve watched ant lions often, but never knew this part of their life story. What is the function of the mouth cavity? Is there no internal digestive system at all? Does the digested stuff go right into the blood? Are there any other insects/animals you know of without internal digestive systems? Poor Mary. Too many questions!

    August 14, 2014 at 2:31 pm

    • Here’s some info from a source, http://www.antlionpit.com :

      What happens to all the food an antlion larva consumes during its life? Do antlions “go to the bathroom”? Yes and no. Antlions excrete some fluid during their larval life. If you keep antlions as pets you might notice small “sugar lumps” in the sand; these are merely sand grains stuck together from excreted fluid (Mansell 2001). But the antlion’s digestive tract lacks an external opening for solid waste, so feces accumulate within its body for the entire larval stage—up to three years! Some of the waste is processed into silk for later use during the pupal stage (Arnett 1985, 249-250); the remainder is voided by the adult when it emerges from the cocoon.

      August 14, 2014 at 2:57 pm

  3. Hi Kathie,
    I’m afraid I don’t know most of your questions’ answers! I suppose the mouth cavity is just a receptacle for what it takes in through its mandibles…and I’m not familiar with the details of their digestive system, I’m afraid. I’ve read both that the waste is excreted before pupation and that it’s excreted by the emerging adult, much like butterflies, etc. I don’t know which is correct, which is why I didn’t mention it in the post! I’ll see if I can find any more details for you. I’d say your more than naturally curious!

    August 14, 2014 at 2:55 pm

  4. Susan Holland

    Pretty cool, and very strange. And of course, now I want to see a picture of it in its winged stage!

    August 15, 2014 at 3:15 am

    • Yes, me too! I’ve never knowingly seen one to photograph!

      August 15, 2014 at 11:53 am

  5. Irma Graf

    You are amazing, Mary! This post tops them all! (Well, maybe not, they are always all good…)

    August 15, 2014 at 9:07 pm

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