A butterfly's wings can have many jobs besides keeping the insect high up in the air. They may be used to attract mates, or to warn potential attackers to stay away. All of these roles, though, depend on their unchanging colouration. This plays into the idea that butterfly wings are dead tissue, like a bird's feathers. In fact, that's not true. For example, in some species males' wings have special cells releasing some chemicals which attract females.
Nanfang Yu, a physicist at Columbia University, in New York, has been looking into the matter. Together with Naomi Pierce, a butterfly specialist at Harvard University, he has now shown, in a paper published in Nature Communications in February, 2020, that butterfly wings are, indeed, very much alive.
In their experiments, the two researchers used a laser(激光) to heat up spots on the wings of dozens of butterfly species. When the temperature of the area under the laser reached 40℃ or so, the insects responded within seconds by doing things that stopped their wings heating up further. These actions included a butterfly turning around to minimize its profile to the laser, moving its wings up and down or simply walking away.
Butterflies engaged in all of these heat-minimising activities even when the researchers blindfolded them. That suggested the relevant sensors were on the wings themselves. Dr Yu and Dr Pierce therefore searched those wings for likely looking sensory cells. They found some, in the form of neurons(神经元) that were similar to heat detectors known from other insects. They also uncovered disc-shaped cells that appeared to be similar to pressure-sensitive neurons. They guess that these are there to detect deformation of the wing—information an insect could use to control its flight pattern.
The third discovery they made to contradict the "dead wing" idea was that some butterfly wings have a heartbeat. A butterfly's wings have veins(静脉). These carry a bloodlike liquid which, researchers have now found in males, shows a pulse(脉搏) of several dozen beats per minute. The source of this pulse appears to be the scent(气味) pad, a dark spot on the wings that produces the female-attracting chemicals. Apparently, this "wing heart" acts as a pump that helps bloodlike liquid through the scent pad.
In all their experiments simulating different environmental conditions, Dr Yu and Dr Pierce consistently found that, different parts of the wing are covered by different sorts of scales(鳞屑). In particular, tubes pass through scales over the scent pads. This improves their ability to spread heat away and helps keep the living parts of a butterfly's wings alive.
