Sometimes, not even repellants can put them at bay … A group of researchers from the California Institute of Technology (Caltech) has studied the behavior of pesky bugs and has concluded that their “fresh blood” detection technique it is more sophisticated than previously thought.
According to experts, when the females of these diptera need to feast to lay their eggs – the males do not sting – they use a triple “technology”: olfactory, visual and thermal. But how do they combine it?
In order to find out, the Caltech scientists first placed 20 specimens in a wind tunnel and observed that, predictably, they followed the smell of CO2, exhaled by humans and other mammals. What surprised them is that, always in the presence of this gas, they were also attracted by the lure of dark objects, as if they associated both stimuli.
Then they tested the mosquitoes’ sensitivity to thermal information. To do this, they impregnated two transparent glass objects with a chemical that allowed to regulate the temperature. Well, the insects flew towards the object that was at 37 ºC , approximately the temperature of the human body, without the need for CO2. This showed that visual and thermal stimuli are independent.
The attack sequence would be as follows: between 50 and 10 meters away, the mosquitoes smell the CO2; between 5 and 15 meters, they see their victim , and when they get even closer, less than a meter, they are also guided by the heat that it emits. The study has been published in the journal Current Biology .
