The long, elongated hindwings, the ribbon-like "tails" that descend from the hindwings of moon moths, have long attracted the attention of scientists and nature lovers. These graceful structures appear to be designed purely for beauty, but biologists have recently begun to realize what factors are actually behind their appearance.
It turns out that such "tails" are the result not only of evolutionary pressure from predators such as
bats, but also a consequence of specific climatic conditions, especially long periods of warm and stable weather.
These "tails" on the hind wings of moths, which look like silk ribbons or thin snake tongues, can be safely put on a par with other striking evolutionary structures: the single tusk of the narwhal, the peacock tail, the ornamental plumage of
birds of paradise or the giant whiskers of some beetles.
All of these traits seem excessive and impractical at first glance, but in reality they serve important purposes - be it defense, attracting mates, or imitating other species. In the case of moths, it is a special balance between effective defense and physical endurance.
According to behavioral ecologist Juliette Rubin of the Smithsonian Tropical Research Institute in Panama, tails in moon moths (family Saturniidae) have arisen independently at least five times during evolution in different subgroups.
This phenomenon is called convergent evolution - where different species arrive at similar solutions independently of each other when faced with similar environmental challenges. This suggests that long tails do bring an adaptive advantage.
Photo: sciencenews.org
Rubin and her colleagues published their findings on May 7 in the journal Proceedings of the Royal Society B." For the first time in the scientific literature, the relationship between climate features - primarily stable warm conditions - and the development of extremely long tails in moth wings has been so clearly traced.
The study authors used photos posted by volunteers on the iNaturalist science platform to map the distribution of morphological traits and correlate it with climatic and biogeographic data.
It turned out that moths living in warm regions with mild climates, where temperature fluctuations are small, are much more likely to have pronounced long "tails".
Under such conditions, larvae spend more time actively feeding without being stressed by cold or sudden changes in weather. This allows them to accumulate more energy and resources needed to form more complex and larger structures in the adult stage. Thus, temperature does not affect the larvae directly, but through the duration and quality of larval development.
The longer the caterpillar can feed and grow quietly, the more likely it is that at the adult (adult form) stage it will have not just a standard wing, but a truly decorative, effective and perhaps even luxurious "tail". This is a kind of investment in the final, reproductive phase of a moth's life.
However, the aesthetic component is not the main thing. Experiments conducted earlier by Rubin showed that the curved "tails" have practically no effect on mating, which means that they are not a sexual trait, as, for example, the tail of the peacock. Their main function is defense against predators, primarily bats, which use
echolocation to hunt in the dark.
When a long-tailed moth flies, the vibrations of these thin appendages create an acoustic and visual "noise" that confuses bats. A predator may miss or attack an inconsequential body part without fatally damaging the moth.
Interestingly, the moths themselves lack hearing: they are unable to perceive echolocation signals and do not emit ultrasonic "warnings" like some nocturnal butterflies do. All they can do is rely on the shape and movement of their wings to fool a predator. This makes "tails" especially important in environments where no other means of defense is available.
The question of the costs of developing such elongated wing trailing edges remains open. As Rubin notes, no convincing evidence has yet been found that they severely degrade aerodynamics or increase energy consumption during flight.
Photo: gazeta.ru
However, it is quite possible that the value of such appendages is expressed in another way - in additional resources required for their growth and in a longer period of larval development. This means that the development of such structures becomes possible only under favorable environmental conditions.
The results of the study raise important questions about how climate affects evolutionary diversity. Global warming and unstable weather patterns may change both the duration of developmental phases in insects and the availability of resources. This, in turn, could affect the frequency of complex structures such as "tails" in moon moths. They may become rare or disappear altogether if conditions no longer support their development.
Thus, the wings and tails of moon moths are not just an amazing example of natural beauty. They are the result of a multi-layered interaction of climate, defense against predators, physiology, and evolutionary compromises. Studying them helps us to better understand exactly how unusual features are formed in living organisms and what role the environment plays in this process.
Juliette Rubin's research not only answers important scientific questions, but also breaks new ground in exploring how a changing world affects
evolution - including in its most graceful and enigmatic inhabitants.