Spanish Bayonet

By William T. Hathaway

Spanish Bayonet (Yucca filamentosa)

In one of my former articles I had written about the relationship between the Spanish bayonet (Yucca filamentosa) plant and the yucca moth. My picture of the Spanish bayonet flower, with its embedded yucca moths, was unsatisfactory. The clinging moths were scarcely visible. After having scanned the same 35 mm slide at a higher percentage magnification, two moths are now quite visible.

The Peterson Field Guide to the Moths of Eastern North America informs its readers that female yucca moths puncture the pistil (female floral organ) and insert one egg per puncture. The moths then pack pollen into the opening; this insures pollination of the flower and a seed supply for the yucca moth's larvae to feed on. Another source of information indicates that yuccas and yucca moths have a mutualistic relationship: the yucca plants need the moths for pollination, and the yucca moths need yucca seeds as food for its young. The mutual dependence is so strong that likely both yucca plants and the yucca moths will become extinct if either falters.