In effect, each "twig" of the "thorn
bush" is ONE insect captured repeatedly along its flight path. Each thorn is the same fly caught by the repeating "flashing" of the light.
As you know mains power is alternating at 50
cycles/second.This means that mains lighting is flickering though we
are not normally aware of it. By leaving the lens open for say 1/5th second - it will
be like the camera flash going off 10 times As the insect flies through the
picture - it get illuminated with each "flash" of the mains lighting. This effect is also quite visible to the naked eye.
In the second photo - the orange, fatter streak is a moth
