You must have seen insects buzzing around a glowing lamp or bulb in your homes. The surprising aspect is that it is only the male insects that get attracted towards light. Moreover, insects are not attracted equally to all sources of light. Do you know why this happens?
The attraction of insects to light has been a subject of interest to researchers since Aristotle’s time. In the late nineteenth century, this phenomenon was studied in great detail by S.W. Frost of Pennsylvania University, U.S.A. Later, from an extensive study of this subject, a French entomologist, J.H. Fabre was able to provide a proper explanation.
Fabre put forth the theory that certain radiations coming out from the light source are responsible for the attraction of insects. This has now been confirmed by some experiments that a series of narrow bands of infrared radiations emitted by the source of light, produce the attraction for insects. This study was conducted on moths.
There is a gland at the tip of the female’s abdomen from which it releases some acetate molecules. These are called pheromone or sex scent. This chemical emits some infrared radiations which spread through air. The male moth, flying at some distance from the female, picks up these radiations and gets attracted towards the female.
The most acute sense of smell exhibited in nature is that of the male emperor moth (Eudia pavonia) which according to German experiments in 1961, can detect the sex attachment of the female at a distance of almost 11 km. Some moths get attracted towards light under the impression that some female moths are there. Thus the search for the female leads it to the light.
Candle lights emit sufficient amount of such radiations, thus attracting a lot of male insects. Insects are also attracted to street lights for the same reason.
It has been found from different studies that the pheromones of different insects are not alike. That is why all insects are not equally attracted towards light. Similar is the case with different light sources. If a light source does not produce these infra-red radiations, insects will not be attracted towards it. This process of insect communication is very complicated and needs sophisticated equipment for study.