Mosquitos have few redeeming qualities. They seem to enjoy buzzing in innocent bystanders’ ears and their bites stay itchy and annoying for days on end.
Beyond these trivial annoyances, however, mosquitos are also notorious carriers and spreaders of disease. Rather unbelievably, it’s estimated that diseases spread via mosquitoes have killed 52 billion humans since the beginning of time. If true, that statistic would mean mosquitoes have killed close to half of all humans that have ever lived! And you thought that itchy bite on your leg was bad.
Now, a groundbreaking new study just released by the University of California, Irvine has made a discovery that very well may revolutionize how people repel and avoid mosquitoes. Mosquitoes that are active at night and bite people nocturnally are attracted to and repelled by different colors of light at different times of the day in comparison to mosquito variations that primarily bite people during the day.
The research team says that these revelations could lead to new light-centric ways to repel certain mosquito variations at certain times of the day.
More specifically, researchers studied the daytime-active Yellow Fever mosquito species (Aedes aegypti) and the nocturnal Anopheles coluzzi mosquito species (a frequent carrier of malaria). These two species displayed differing reactions and responses to ultraviolet light and other light colors. Additionally, light preference between individual mosquitoes appears to vary greatly depending on various factors including the mosquito’s gender and species, the time of day, and light color.
“Conventional wisdom has been that insects are non-specifically attracted to ultraviolet light, hence the widespread use of ultraviolet light “bug zappers” for insect control. We find that day-biting mosquitoes are attracted to a wide range of light spectra during the daytime, whereas night-biting mosquitoes are strongly photophobic to short-wavelength light during the daytime,” explains principal investigator Todd C. Holmes, Ph.D., a professor in the Department of Physiology and Biophysics at the UCI School of Medicine, in a university release. “Our results show that timing and light spectra are critical for species-specific light control of harmful mosquitoes.”
Day-biting mosquitoes, especially females in search of extra blood for their fertilized eggs, tend to be drawn toward all forms of daytime light regardless of intensity. Night-biting mosquitoes, on the other hand, try their best to avoid ultraviolet and blue light during the day.
Previous work conducted in professor Holmes’ lab had already located and identified both the light sensors and circadian molecular mechanisms controlling light-responsive behaviors (attraction/avoidance) among fruit flies. Now, fruit flies are closely related to mosquitoes, so disruption of mosquitoes’ circadian clocks should disrupt their light-responsive actions.
As of right now, there are no available light-based mosquito control options that account for these fluctuations in how different mosquitoes react to different forms of light. Professor Holmes is optimistic that may change in the future.
“Light is the primary regulator of circadian rhythms and evokes a wide range of time-of-day specific behaviors,” professor Holmes concludes. “By gaining an understanding of how insects respond to short wavelength light in a species-specific manner, we can develop new, environmentally friendly alternatives to controlling harmful insects more effectively and reduce the need for environmentally damaging toxic pesticides.”The full study can be found here, published in Current Biology.