Why do moths fly towards the light?
This is another well-known and widespread phenomenon, the reasons for which few people think about. Have you seen moths flying towards the light bulb? Why do you think they do it? Why do they need bright light? Why do they often fly towards their death?
The situation when a butterfly (and more often a moth) flies towards the light is called phototactis. The reaction to light in insects is quite common. You may have noticed how cockroaches scatter (negative phototactis) if you turn on the light in the kitchen.
There is no consensus on why butterflies fly to the light. Let's start with the first theory that can explain this phenomenon.
Nocturnal insects navigate by the moon and stars during flights. These light sources are far from the Earth, and the rays emitted by them are almost parallel. In order to fly in a straight line, the insect maintains a constant angle between the direction of its movement and the direction to the luminary. And the rays of light from artificial sources diverge in all directions.
Therefore, maintaining a constant angle with respect to them, the insect flies not in a straight line, but in a logarithmic (isogonal) spiral. If the spiral intersects the rays at an acute angle, it will contract towards the source of the rays; if at an obtuse angle, it will diverge. If the angle is right, then the spiral will degenerate into a circle.
Indeed, following the flight of insects, one can notice that usually they do not fly directly to the light source, but approach it in a converging spiral or fly in circles. In fact, insects tend to move straight, but the laws of geometrical optics keep them near the lamp. Sometimes, however, they turn sharply to the side, but the new direction again twists into a spiral. If the insect has chosen a course at an angle more than a straight one, then it will fly in a divergent spiral until it loses sight of the light source. We do not observe such moths near the lamps.
In 1960 G. A. Mazokhin-Porshnyakov suggested that insects fly towards the light, since it is the universal and most reliable indicator of open space. This may explain the special attraction of ultraviolet radiation (insects react especially actively to it), since it is almost not reflected by terrestrial objects. So a butterfly that has flown into a room will beat against the window, heading towards the source of UV radiation - the sun. So falling into a ray of light at night, the insect can perceive the darkness surrounding it as a closed space and, trying to escape, fly towards the light.
Here is another version.
A smooth color transition is perceived as stripes. At the border of white, an even whiter stripe is visible, and at the border of black, an even blacker one. This illusion is caused by lateral inhibition in the retina.
There is an opposite version that moths fly towards the darkest, oddly enough, zone, that is, they want to fly away from the light. This zone near the source, at the border of light and shadow, appears the blackest to the moth due to a common optical illusion known as Mach bands. Due to an optical illusion - Mach bands, it seems to the moth that the darkest darkness is around it - next to the light bulb - and it tries to fly there and flies. We are subject to the same illusion - if we draw a white and gray strip side by side - we will see a black strip between them.
The rectangles seem to be underlined. It seems that the left borders are lighter than the right borders, although they are evenly colored.
The roots of phototactis have not yet been clarified, but it is surprising that even different species of the same genus can react to light differently: some species fly actively towards it, and some do not fly at all.
