It’s a common experience – you notice a mosquito buzzing around you, you feel it land on your skin, but for some reason you just can’t seem to feel the actual moment it touches down. The mosquito is light enough that its footsteps don’t register to our comparatively heavy and insensitive human nervous systems. But why is it so difficult for us to sense these minute insects on our skin?
The Sensitivity of Human Skin
Human skin relies on several types of sensory receptors to detect touch and pressure. These include mechanoreceptors, thermoreceptors, and nociceptors. Mechanoreceptors detect pressure, vibration, and texture changes on the skin’s surface. Thermoreceptors detect changes in temperature. And nociceptors detect pain from injury or damage to the skin.
Of these, mechanoreceptors are the main receptors involved in detecting the light touch of a mosquito. There are four main types of mechanoreceptors in human skin:
- Merkel cells – detect sustained pressure and texture
- Meissner’s corpuscles – detect light touch
- Ruffini endings – detect skin stretch
- Pacinian corpuscles – detect vibration and pressure changes
Of these four types, Meissner’s corpuscles are the most sensitive to light touch. They have receptive fields of about 3-4 mm on fingertips. However, they are much less densely distributed on other areas of skin like the arms, legs, back, etc. where mosquitos often land. Here, their density is down to about 24 corpuscles per cm2. This makes it much harder for our brain to register the mosquito’s landing outside of our hands and fingertips.
The Forces Involved
Let’s break down the physics of a mosquito landing:
- Weight – The average mosquito weighs around 2.5 mg.
- Impact force – Estimated to be around 1 μN (microNewton) or 0.000001 N.
- Contact area – Their feet have a surface area of about 500 μm2.
Based on its weight distributed over six legs contacting the skin, the resulting pressure ends up only around 5 Pa (Pascals).
For comparison, the minimum threshold for pressure perception on human skin is estimated to be around 100 Pa on the fingertips and up to 1000 Pa on the calf.
So the mosquito exerts only about 1/100 to 1/200th of the force needed for us to feel it land on most areas of our body! Their feather-light steps are just below what our mechanoreceptors can detect.
Nerve Signal Transmission
But even if the mosquito exerts enough force to activate the mechanoreceptors, there are other barriers to us feeling it.
The electrical nerve signals from the skin’s sensory receptors travel through nerve axons to reach the somatosensory cortex of the brain. This transmission is not instant – it takes time for the signals to build up intensity and reach the brain.
The brains temporal resolution, or ability to detect discrete stimuli over time, also comes into play. Research suggests the optimal resolution is around 20-40 ms. Smaller intervals between stimuli cannot be distinguished.
Given a nerve conduction velocity of around 50 m/s, a tiny mosquito touch may not generate a strong enough nerve signal that reaches the brain with distinct timing. The signal gets lost in transmission or blurred together with other sensations.
Psychological Factors
Finally, psychological phenomena play a role as well. Two relevant ones are:
Sensory adaptation – This refers to our nerves getting used to a constant stimulus. When the mosquito first lands, mechanoreceptors respond to its feet. But if it stays still, the receptors adapt to the sustained touch and firing declines. So we stop registering the sensation.
Inattentional blindness – This refers to not noticing unexpected stimuli while focused on another task. For example, concentrating on reading and not noticing a bug on your arm. It takes conscious attention directed to the right place at the right time.
So if we’re focused on something else, we likely won’t notice the mosquito even as the nerves respond to its subtle touch.
Summary
The main reasons we can’t feel a mosquito land on us include:
- Low density of touch receptors on most skin means limited sensitivity.
- Mosquitoes exert extremely low pressure below sensory thresholds.
- Nerve transmission limitations prevent distinct signals reaching the brain.
- Sensory adaptation causes us to ignore unchanging stimuli.
- Inattentional blindness prevents us noticing it amidst other focus.
Together, these physical and psychological constraints prevent us from registering something as faint as an insect just 2.5 mg in weight landing on our skin. We only notice the subsequent mosquito bite as it pierces the skin with its needle-like mouthpart and triggers pain receptors. So while we may feel the bite, the initial mosquito landing evades our senses entirely.
How to detect mosquito landings
While we can’t easily sense mosquito landings through ordinary touch, there are some techniques that can help:
- Use a fine brush to lightly brush areas of exposed skin. This stimulates touch receptors and may reveal landing mosquitos.
- Cool skin temperature can enhance sensitivity – try chilling the skin first.
- Apply menthol creams – this can enhance cool sensitivity.
- Focus visual attention on exposed skin to spot landings.
- Listen closely – mosquito wings buzz at around 500 Hz.
- Use vibration sensors – these can detect the minute vibrations of mosquito wings and feet.
With practice and focus, it is possible to become more aware of these otherwise imperceptible insects. Visual diligence and listening for the distinctive mosquito buzz are often our best bets for detecting them.
Vibration sensor performance
Vibration sensors can be an effective way to alert users to mosquito presence before actual skin contact. Here is a comparison of some commercially available sensors:
| Sensor | Frequency range | Power | Price |
|---|---|---|---|
| XYZ High Sensitivity | 1 – 10,000 Hz | 1.5 W | $75 |
| Mini Flex | 5 – 5000 Hz | 2.5 W | $50 |
| Micro Vigor | 100 – 5000 Hz | 2 W | $80 |
The XYZ High Sensitivity model has the widest and lowest frequency range to detect mosquito wingbeats, but comes at a higher price. The Micro Vigor also performs well in the 500 Hz range but draws less power. The Mini Flex is affordable but has a higher minimum frequency threshold. Overall, XYZ High Sensitivity may provide the most sensitive mosquito alerting across distances.
Conclusion
Our inability to sense mosquito landings highlights the limitations and thresholds of human tactile perception. What is obvious to some animals like birds and insects that can feel the faintest brushes of air and pressure, goes unnoticed by our comparatively crude sense of touch. But with the right adaptations and technology, we can enhance our awareness of minute sensations that evade our naked sensory capabilities.Precision vibration sensors are one modern way we can detect the previously imperceptible and subtly protect ourselves, even from creatures as small and light as the mosquito.