Population Control

Today my hip and knees hurt, but I tottered around outside anyway. I couldn’t resist the 72º F. temperature and semi-sunny sky. I made my way slowly and carefully, which gave me plenty of opportunity for noticing details. I was making a mental list of spring clean up chores, one of which is to cut the yucca bloom stalks from last year.

Yucca plants were in the yard when we bought this place almost 39 years ago. They are still here.

We made the mistake of cutting the seed stalks and tossing the over the fence into the pasture. Now yucca colonies are appearing all over the pasture. They make a beautiful spectacle when they bloom each June, tall sentinels adorned with white blossoms.

There’s no telling how many yucca plants we would have if not for nature’s yucca population control method. The yucca blossoms attract yucca moths, which lay their eggs in yucca blossoms. The larva then feed on some but not all of the developing yucca seeds and exit the seedpod by boring tiny holes in the hardened casing. Here you can see two exit holes used by larvae as they emerged.

But that isn’t the whole story. Not only does the yucca moth depend exclusively on the yucca flower for its continued existence, the yucca moth is the yucca’s only pollinator. This symbiotic relationship has enable both species to survive through many millennia. But, if the yucca moth larvae didn’t eat seeds we would be overrun by yucca plants.

Human beings also have symbiotic relationships with various other life forms, but we have conquered many other life forms that would control our population. As more and more diseases and health conditions are conquered, we have reached the point where only war and famine can keep us from totally covering and possibly destroying the earth.

To learn more about the relationship between the yucca plant and the yucca moth, visit http://prairieecologist.com/2010/12/08/the-yucca-and-its-moth/.

Copyright 2014 by Shirley Domer