June — This month, it's antlions

Learn whos hiding at the bottom of some depressions not far from the river.

During a recent visit to one of the prairie remnants in the Twin City Area, staff from FMRs phenology department happened upon some strange conical-shaped depressions in the sand of a trail. At the bottom of two of the small pits were black beetles, both on their backs, thrashing about. Upon closer examination, each beetle was in the deadly grasp of an antlion larva. Antlions are in the family of insects called Myrmeleontidae, which comes from two Greek words Myrmex (ant) and leon (lion).

The antlion larva excavate these depressions, bury themselves, face up, in the soil at the bottom and wait for an ant, beetle, or other insect to fall or stumble in. When this happens the larva grabs the prey with its large spiny jaws and eats it. Some interesting tidbits taken from the web site entitled, The Antlion Pit:

  • The size of the crater has nothing to do with the size of the antlion, but to how hungry the creature is. The longer the insect has gone without food, the larger it makes its crater (Grzimek 1979, 224).
  • Antlions dig bigger pits during a full moon. (Goodenough, McGuire, and Wallace 1993).

Antlion adults, which somewhat resemble damselflies or dragonflies, are rarely seen because they are only active at night. During the day they cling to branches. Females lay eggs in warm sand.

Look for antlion depressions in sandy soils of prairies. Trails on the dry prairie portion of the Hastings Wildlife Management Area are good places to find these fascinating insects. To learn more and to see pictures of antlion adults and larva as well as the pits they dig, visit the Antlion Pit or the Kaweah Oaks information site.