Moths and STDs

Utetheisa ornatrix - a beautiful and chemically protected moth

The artiid moth, Utetheisa ornatrix, is commonly known as the ‘rattlebox moth’ since as a larva it feeds on the rattlebox plant Crotalaria mucronata, so named for the sound produced when the seeds in the pod are shaken.  From this plant, the moth acquires pyrrolizidine alkaloids (PA), chemicals which make the caterpillar distasteful to predators (such as spiders and beetles).  The moths retain these chemicals through pupation to adulthood.   Additionally, males transmit these protective chemicals to females during mating (which can last between 8-9 hours – phew!).  This STD (Sexually Transmitted Defense) allows both the female and her offspring to be better protected from predators.  Amazingly, this nuptial gift of chemical defense lasts through the entire lifetime of the female.  A gift like that puts your Valentine’s day chocolate box to shame.  These beautiful moths are diurnal (day fliers) and brilliantly colored, warning predators of their distastefulness.  I grew up seeing these moths flying around Florida and was thrilled to be able to photograph them during my recent visit.


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