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← Mating frenzies, sperm hoards, and brood raids: the life of a fire ant queen

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Showing Revision 1 created 01/14/2020 by lauren mcalpine .

  1. It’s June, just after a heavy rainfall,
  2. and the sky is filling with creatures
    we wouldn’t normally expect to find there.
  3. At first glance,
    this might be a disturbing sight.
  4. But for the lucky males and females
    of Solenopsis invicta,
  5. otherwise known as fire ants,
    it’s a day of romance.
  6. This is the nuptial flight,

  7. when thousands of reproduction-capable
    male and female ants,
  8. called alates,
    take wing for the first and last time.
  9. But even for successful males
    who manage to avoid winged predators,
  10. this mating frenzy will prove lethal.
  11. And for a successfully mated female,
    her work is only beginning.
  12. Having secured a lifetime supply of sperm
    from her departed mate,

  13. our new queen must now single-handedly
    start an entire colony.
  14. Descending to the ground,
  15. she searches for a suitable spot
    to build her nest.
  16. Ideally, she can find somewhere
    with loose, easy-to-dig soil—
  17. like farmland
    already disturbed by human activity.
  18. Once she finds the perfect spot,
    she breaks off her wings—
  19. creating the stubs
    that establish her royal status.
  20. Then, she starts digging
    a descending tunnel ending in a chamber.
  21. Here the queen begins laying her eggs,
    about ten per day,
  22. and the first larvae hatch within a week.
  23. Over the next three weeks,
  24. the new queen relies on a separate batch
    of unfertilized eggs
  25. to nourish both herself and her brood,
  26. losing half her body weight
    in the process.
  27. Thankfully, after about 20 days,
  28. these larvae grow
    into the first generation of workers,
  29. ready to forage for food
    and sustain their shrunken queen.
  30. Her daughters
    will have to work quickly though—

  31. returning their mother
    to good health is urgent.
  32. In the surrounding area,
  33. dozens of neighboring queens
    are building their own ant armies.
  34. These colonies
    have peacefully coexisted so far,
  35. but once workers appear,
  36. a phenomenon known as brood-raiding
  37. Workers from nests
    up to several meters away
  38. begin to steal offspring
    from our queen.
  39. Our colony retaliates,
  40. but new waves of raiders
    from even further away
  41. overwhelm the workers.
  42. Within hours, the raiders have taken
    our queen’s entire brood supply
  43. to the largest nearby nest—
  44. and the queen’s surviving daughters
    abandon her.
  45. Chasing her last chance of survival,
  46. the queen follows the raiding trail
    to the winning nest.
  47. She fends off other losing queens
    and the defending nest’s workers,
  48. fighting her way
    to the top of the brood pile.
  49. Her daughters help their mother succeed
    where other queens fail—
  50. defeating the reigning monarch,
    and usurping the brood pile.
  51. Eventually,
    all the remaining challengers fail,
  52. until only one queen—
    and one brood pile— remains.
  53. Now presiding over several hundred workers
    in the neighborhood’s largest nest,

  54. our victorious queen begins
    aiding her colony in its primary goal:
  55. reproduction.
  56. For the next several years,
    the colony only produces sterile workers.
  57. But once their population
    exceeds about 23,000,
  58. it changes course.
  59. From now on, every spring,
  60. the colony will produce
    fertile alate males and females.
  61. The colony spawns these larger ants
    throughout the early summer,
  62. and returns to worker production
    in the fall.
  63. After heavy rainfalls,
    these alates take to the skies,
  64. and spread their queen’s genes
    up to a couple hundred meters downwind.
  65. But to contribute
    to this annual mating frenzy,

  66. the colony must continue to thrive
    as one massive super-organism.
  67. Every day, younger ants feed the queen
    and tend to the brood,
  68. while older workers
    forage for food and defend the nest.
  69. When intruders strike,
  70. these older warriors fend them off
    using poisonous venom.
  71. After rainfalls,
    the colony comes together,
  72. using the wet dirt to expand their nest.
  73. And when a disastrous flood
    drowns their home,
  74. the sisters band together
    into a massive living raft—
  75. carrying their queen to safety.
  76. But no matter how resilient,

  77. the life of a colony must come to an end.
  78. After about 8 years,
    our queen runs out of sperm
  79. and can no longer replace dying workers.
  80. The nest’s population dwindles,
    and eventually,
  81. they’re taken over
    by a neighboring colony.
  82. Our queen’s reign is over,
    but her genetic legacy lives on.