Out of all the myriad ways that species in the animal kingdom use to attract mates—birds display brilliantly colored plumage, insects make music, bees do dances, glow worms use light, and the pufferfish goes as far as creating geometric circles in the seabed—none is truly as strange as the one displayed by the bella moth.
According to a recent study, the bella moth (Utetheisa ornatrix) has reportedly evolved to use the toxins of a particular plant they consume during caterpillarhood to not only safeguard themselves (and later their eggs) against predators but also attract potential mates.
The leaves and seeds of the rattlebox plant are laden with a particular kind of bitter-tasting toxin known as pyrrolizidine alkaloids. Widely shunned by the rest of the foragers, the rattlebox is the preferred food source of the bella moth.
Not only does this brightly colored moth have immunity against this toxin—which, mind you, is one of the leading causes of accidental poisoning-related deaths in cattle—it can actually metabolize and use it to achieve its own ends.
Bella moths are prevalent across large parts of eastern North America, Central America, and the Caribbean, and they exhibit diurnal activity patterns. Unlike many other nocturnal species that rely on darkness for concealment from predators, bella moths deliberately flaunt their presence.
Adorned with vibrant hues like radiant pink, pearl, onyx, and sulfur yellow scales on their wings, they stand out conspicuously, easily catching the attention of birds and carnivorous insects from afar. Any predator that attempts to prey upon a bella moth soon realizes its error.
“Banana spiders will cut them out of their webs,” explains study co-author Andrei Sourakov. “When caught, they produce foaming liquid that tastes bad made almost entirely out of alkaloids.” He also points out how wolf spiders and birds, common moth predators, do everything possible to avoid this poisonous moth.
How bella moths use poison to attract mates
When female bella moths are ready to mate, they emit a cloud of aerosolized alkaloids acquired from the plants they consume as caterpillars. Males, drawn to this scent, reach the female and engage in a brief yet intricate ritual.
During this ritual, they delicately touch the female’s head with two fluffy and retractable structures resembling dandelions. Each filament of these structures contains pyrrolizidine alkaloids.
If the female deems the male’s alkaloid supply sufficient in quantity and quality, they proceed to mate. After mating, the male leaves behind a spermatophore containing sperm and additional alkaloids. The female uses these compounds and alkaloids from her own reserves to imbue the resulting eggs with toxins.
Such biparental egg protection is uncommon among insects. Initially observed in bella moth adults in 1989, it represents the sole known instance of a male moth or butterfly investing chemical resources in its offspring.
This study was published in the journal PNAS.
