Aedes aegypti mosquito
It’s late spring. It’s the time to have an evening drink in the garden, a relaxing walk in the forest filled with singing birds and to open the windows during the first warm nights.
Bzzzz…
But the peaceful mood is gone when we hear a mosquito flying past our ear.
Our best chance of killing the mosquito seems to be when they land on us, hopefully before they “bite”*.
Why are they so difficult to swat when flying?
Recently researchers from the Netherlands and Germany decided to answer this question using high resolution recordings of these insects, both flying undisturbed and when being “attacked” by a mechanical swatter.
The main conclusion is that it’s difficult to catch flying mosquito largely because their flight is very erratic. They change course (turn) often and within half a second may be more than 10 cm away from the location one would expect based on their current flight path. This is true even if there is nothing trying to hit them.
However, this baseline tactic is somewhat different and can be adjusted in different ways in different mosquito species.
Researchers studied two species: Anopheles coluzzii, an African species (that has cousins around the world) that is active during the night; and Aedes aegypti, a species that is present in many regions around the world and hunts during the day.
Anopheles mosquitos, in addition to erratic flight, also use active escape maneuvers to avoid collisions with the swatter, especially if there is some light. However, these mosquitos actually avoided collisions most effectively in darkness. Some of the escapes could have been aided (directly or as a cue) by the air flow caused by the swatter, but the main tactic seems to be to increase their speed. This, adds extra unpredictability to their already erratic flight.
Aedes mosquitos, even though they change the flight direction less often, are much better at avoiding the swatter, mainly due to their higher baseline speed and therefore high baseline flight unpredictability. Surprisingly, they seem to rely less on active escape maneuvers, but they do use visual cues and/or air movement to avoid collisions with a swatter. The more light there is, the more often they used fast escapes to avoid the swatter (they don’t fly in darkness).
Although the escape tactics of the two mosquitos clearly differ it is yet unclear why it is so.
All in all, it might just be easier to ignore mosquitos (in countries where they don’t spread diseases) than to try to kill them.
* Mosquitos don’t really bite. They use their needle-like mouth parts to pierce the skin. Only females drink blood. They need it to develop their eggs. Males feed on nectar and other sugar sources. Females can also drink nectar to sustain themselves.
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Photo: Muhammad Mahdi Karim – Own work, GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=9556152